Showing papers in "Applied Biochemistry and Biotechnology in 2010"

Cultivation of green algae Chlorella sp. in different wastewaters from municipal wastewater treatment plant.

Abstract: The objective of this study was to evaluate the growth of green algae Chlorella sp. on wastewaters sampled from four different points of the treatment process flow of a local municipal wastewater treatment plant (MWTP) and how well the algal growth removed nitrogen, phosphorus, chemical oxygen demand (COD), and metal ions from the wastewaters. The four wastewaters were wastewater before primary settling (#1 wastewater), wastewater after primary settling (#2 wastewater), wastewater after activated sludge tank (#3 wastewater), and centrate (#4 wastewater), which is the wastewater generated in sludge centrifuge. The average specific growth rates in the exponential period were 0.412, 0.429, 0.343, and 0.948 day(-1) for wastewaters #1, #2, #3, and #4, respectively. The removal rates of NH4-N were 82.4%, 74.7%, and 78.3% for wastewaters #1, #2, and #4, respectively. For #3 wastewater, 62.5% of NO3-N, the major inorganic nitrogen form, was removed with 6.3-fold of NO2-N generated. From wastewaters #1, #2, and #4, 83.2%, 90.6%, and 85.6% phosphorus and 50.9%, 56.5%, and 83.0% COD were removed, respectively. Only 4.7% was removed in #3 wastewater and the COD in #3 wastewater increased slightly after algal growth, probably due to the excretion of small photosynthetic organic molecules by algae. Metal ions, especially Al, Ca, Fe, Mg, and Mn in centrate, were found to be removed very efficiently. The results of this study suggest that growing algae in nutrient-rich centrate offers a new option of applying algal process in MWTP to manage the nutrient load for the aeration tank to which the centrate is returned, serving the dual roles of nutrient reduction and valuable biofuel feedstock production.

Culture of Microalgae Chlamydomonas reinhardtii in Wastewater for Biomass Feedstock Production

Abstract: The objective of this research was to develop large-scale technologies to produce oil-rich algal biomass from wastewater. The experiments were conducted using Erlenmeyer flasks and biocoil photobioreactor. Chlamydomonas reinhardtii was grown in artificial media and wastewaters taken from three different stages of the treatment process, namely, influent, effluent, and centrate. Each of wastewaters contained different levels of nutrients. The specific growth rate of C. reinhardtii in different cultures was monitored over a period of 10 days. The biomass yield of microalgae and associated nitrogen and phosphorous removal were evaluated. Effects of CO(2) and pH on the growth were also studied. The level of nutrients greatly influenced algae growth. High levels of nutrients seem to inhibit algae growth in the beginning, but provided sustained growth to a high degree. The studies have shown that the optimal pH for C. reinhardtii is in the range of 7.5. An injection of air and a moderate amount of CO(2) promoted algae growth. However, too much CO(2) inhibited algae growth due to a significant decrease in pH. The experimental results showed that algal dry biomass yield reached a maximum of 2.0 g L(-1) day(-1) in the biocoil. The oil content of microalgae of C. reinhardtii was 25.25% (w/w) in dry biomass weight. In the biocoil, 55.8 mg nitrogen and 17.4 mg phosphorus per liter per day were effectively removed from the centrate wastewater. Ferric chloride was found to be an effective flocculent that helps the algae settle for easy harvest and separation from the culture media.

Ligninolytic fungal laccases and their biotechnological applications

Abstract: Lignin is amorphous in nature, lacks stereoregularity, and is not susceptible to hydrolytic attack. Despite its resistant nature, it is however degraded by various microorganisms, particularly, white-rot fungi. Such fungi are capable of extracellular production of lignin peroxidase, manganese peroxidase, and laccase, the three major enzymes associated with ligninolysis. Though all white-rot fungi do not produce all the three enzymes, laccase occupies an important place in ligninolysis. Laccase belongs to a diverse group of enzymes called oxidoreductases and is also known as benzenediol: oxygen oxidoreductase. They have low substrate specificity. The copper-containing enzyme laccase has been detected in a variety of organisms such as bacteria, fungi, plants, and insects. Mostly, these are extracellular proteins, although intracellular laccases have also been detected in some fungi and insects. Fungal laccases are believed to play a variety of roles, such as, morphogenesis, pathogenesis, and lignin degradation. As an oxidase, laccase is used in many agricultural, industrial, and medicinal applications. Current investigations are focused on laccase-based biooxidation, biotransformation, biosensor, and enzymatic synthesis of organic compounds. By enhancing laccase production using different physiochemical parameters, better understanding of the mechanism for the reactions of interest, and optimizing the catalytic activity of laccase, it can be used in a better way in diverse fields of biotechnology.

Structural characterization and comparison of switchgrass ball-milled lignin before and after dilute acid pretreatment.

Abstract: To reduce the recalcitrance and enhance enzymatic activity, dilute H2SO4 pretreatment was carried out on Alamo switchgrass (Panicum virgatum). Ball-milled lignin was isolated from switchgrass before and after pretreatment. Its structure was characterized by 13C, HSQC, and 31P NMR spectroscopy. It was confirmed that ball-milled switchgrass lignin is of HGS type with a considerable amount of p-coumarate and felurate esters of lignin. The major ball-milled lignin interunit was the β-O-4 linkage, and a minor amount of phenylcoumarin, resinol, and spirodienone units were also present. As a result of the acid pretreatment, there was 36% decrease of β-O-4 linkage observed. In addition to these changes, the S/G ratio decreases from 0.80 to 0.53.

Oil Accumulation via Heterotrophic/Mixotrophic Chlorella protothecoides

Abstract: Microalgal oil is a potential energy source because it can be easily converted to fatty acid methyl ester or hydrocarbon type of diesel, and it is produced with relatively higher productivity compared with oil from plants and animals. Heterotrophic growth of microalgae is superior due to its high final product concentration; however, the cost of the raw materials is unacceptable if sugar is utilized as the carbon source. The aim of this study is to optimize the lipid accumulation of Chlorella protothecoides by using carbon sources other than glucose in heterotrophic and mixotrophic cultures. Different factors such as different carbon sources, carbon to nitrogen ratio, initial pH level, salinity, and rotational speed are studied in affecting the cell growth and the oil accumulation. Our experiments revealed that the heterotrophic and mixotrophic cultures of C. protothecoides grew better than autotrophic cultures. C. protothecoides can grow on glycerol or acetate, as well as on glucose. Several stress factors were confirmed or discovered to significantly increase the lipid content of microalgae cells. The replacement of glycerol and acetate as carbon sources for microalgae cultivations provides potential for waste utilization: glycerol from biodiesel industry and acetate from biohydrogen production.

Evaluation of High Solids Alkaline Pretreatment of Rice Straw

Abstract: Fresh-harvested, air-dried rice straw was pretreated at a water content of 5 g H2O/g straw using sodium hydroxide (NaOH) and compared to pretreatment at 10 g H2O/g straw by hydrated lime (Ca(OH)2). Full factorial experiments including parallel wash-only treatments were completed with both sources of alkali. The experiments were designed to measure the effects of alkaline loading and pretreatment time on delignification and sugar yield upon enzymatic hydrolysis. Reaction temperature was held constant at 95°C for lime pretreatment and 55°C for NaOH pretreatment. The range of delignification was 13.1% to 27.0% for lime pretreatments and was 8.6% to 23.1% for NaOH pretreatments. Both alkaline loading and reaction time had significant positive effects (p < 0.001) on delignification under the design conditions, but only alkaline loading had a significant positive effect on enzymatic hydrolysis. Treatment at higher temperature also improved delignification; delignification with water alone ranged from 9.9% to 14.5% for pretreatment at 95°C, but there was little effect observed at 55°C. Post-pretreatment washing of biomass was not necessary for subsequent enzymatic hydrolysis. Maximum glucose yields were 176.3 mg/g dried biomass (48.5% conversion efficiency of total glucose) in lime-pretreated and unwashed biomass and were 142.3 mg/g dried biomass (39.2% conversion efficiency of total glucose) in NaOH-pretreated and unwashed biomass.

Chlorella minutissima--a promising fuel alga for cultivation in municipal wastewaters.

Abstract: It is imperative to slash the cost of algal oil to less than $50 bbl−1 for successful algal biofuel production. Use of municipal wastewater for algal cultivation could obviate the need for freshwater and the nutrients—N and P. It would also add CO2 through bacterial activity. Chlorella minutissima Fott et Nova dominated the entire phycoflora year around and through each stage of the wastewater treatment at the oxidation pond system of Wazirabad (Delhi) in India. The ability to grow so profusely in such varied and contrasting situations made this alga unique. Besides pollution tolerance, it grew heterotrophically in dark under acidic conditions and as a mixotroph in presence of light over a range of organic C substrates. It could utilize both ammoniacal and nitrate nitrogen, survived anaerobicity, 5% NaCl and −10 bar of osmotic stress. C. minutissima grew at pH 4–11 and raised the pH set initially by 1 to 3 units in 7.5 h. It showed gigantism and largely kept afloat in presence of utilizable organic carbon, while flocculated in mineral medium and on aging. The alga also possessed potential for biofuel production. The studied parameters indicate why C. minutissima was a potential biomass builder in municipal sewage and could be used to determine which other alga(e) may serve the purpose.

Phytochelatins: peptides involved in heavy metal detoxification.

Abstract: Phytochelatins (PCs) are enzymatically synthesized peptides known to involve in heavy metal detoxification and accumulation, which have been measured in plants grown at high heavy metal concentrations, but few studies have examined the response of plants even at lower environmentally relevant metal concentrations. Recently, genes encoding the enzyme PC synthase have been identified in plants and other species enabling molecular biological studies to untangle the mechanisms underlying PC synthesis and its regulation. The present paper embodies review on recent advances in structure of PCs, their biosynthetic regulation, roles in heavy metal detoxification and/or accumulation, and PC synthase gene expression for better understanding of mechanism involved and to improve phytoremediation efficiency of plants for wider application.

Influence of High Solid Concentration on Enzymatic Hydrolysis and Fermentation of Steam-Exploded Corn Stover Biomass

Abstract: Steam-exploded corn stover biomass was used as the substrate for fed-batch separate enzymatic hydrolysis and fermentation (SHF) to investigate the solid concentration ranging from 10% to 30% (w/w) on the lignocellulose enzymatic hydrolysis and fermentation. The treatment of washing the steam-exploded material was also evaluated by experiments. The results showed that cellulose conversion changed little with increasing solid concentration, and fermentation by Saccharomyces cerevisiae revealed a nearly same ethanol yield with the water-washed steam-exploded corn stover. For the washed material at 30% substrate concentration, i.e., 30% water insoluble solids (WIS), enzymatic hydrolysis yielded 103.3 g/l glucose solution and a cellulose conversion of 72.5%, thus a high ethanol level up to 49.5 g/l. With the unwashed steam-exploded corn stover, though a cellulose conversion of 70.9% was obtained in hydrolysis at 30% solid concentration (27.9% WIS), its hydrolysate did not ferment at all, and the hydrolysate of 20% solid loading containing 3.3 g/l acetic acid and 145 mg/l furfural already exerted a strong inhibition on the fermentation and ethanol production.

Extraction and Characterization of Chitin, Chitosan, and Protein Hydrolysates Prepared from Shrimp Waste by Treatment with Crude Protease from Bacillus cereus SV1

Abstract: Chitin is a polysaccharide found in abundance in the shell of crustaceans. In this study, the protease from Bacillus cereus SV1 was applied for chitin extraction from shrimp waste material of Metapenaeus monoceros. A high level of deproteinization 88.8% +/- 0.4 was recorded with an E/S ratio of 20. The demineralization was completely achieved within 6 h at room temperature in HCl 1.25 M, and the residual content of calcium in chitin was below 0.01%. (13)C CP/MAS-NMR spectral analysis of chitin prepared by the enzymatic deproteinization of shrimp wastes was found to be similar to that obtained by alkaline treatment and to the commercial alpha-chitin. The degree of N-acetylation, calculated from the spectrum, was 89.5%. Chitin obtained by treatment with crude protease from B. cereus was converted to chitosan by N-deacetylation, and the antibacterial activity of chitosan solution against different bacteria was investigated. Results showed that chitosan solution at 50 mg/mL markedly inhibited the growth of most Gram-negative and Gram-positive bacteria tested. Furthermore, the antioxidant potential of the protein hydrolysates obtained during enzymatic isolation of chitin was evaluated using various in vitro assays. All the samples exerted remarkable antioxidant activities. These results suggest that enzymatic deproteinization of the shrimp shell wastes, using B. cereus SV1 protease, could be applicable to the chitin production process.

Evaluation of Biogas Production Potential by Dry Anaerobic Digestion of Switchgrass–Animal Manure Mixtures

Abstract: Anaerobic digestion is a biological method used to convert organic wastes into a stable product for land application with reduced environmental impacts. The biogas produced can be used as an alternative renewable energy source. Dry anaerobic digestion [>15% total solid (TS)] has an advantage over wet digestion (<10% TS) because it allows for the use of a smaller volume of reactor and because it reduces wastewater production. In addition, it produces a fertilizer that is easier to transport. Performance of anaerobic digestion of animal manure-switchgrass mixture was evaluated under dry (15% TS) and thermophilic conditions (55 degrees C). Three different mixtures of animal manure (swine, poultry, and dairy) and switchgrass were digested using batch-operated 1-L reactors. The swine manure test units showed 52.9% volatile solids (VS) removal during the 62-day trial, while dairy and poultry manure test units showed 9.3% and 20.2%, respectively. Over the 62 day digestion, the swine manure test units yielded the highest amount of methane 0.337 L CH4/g VS, while the dairy and poultry manure test units showed very poor methane yield 0.028 L CH4/g VS and 0.002 L CH4/g VS, respectively. Although dairy and poultry manure performed poorly, they may still have high potential as biomass for dry anaerobic digestion if appropriate designs are developed to prevent significant volatile fatty acid (VFA) accumulation and pH drop.

Potential of Crocus sativus (saffron) and its Constituent, Crocin, as Hypolipidemic and Antioxidant in Rats

Abstract: The aim of the present study was to evaluate the hypolipidemic and antioxidant potential of saffron and its active constituent, crocin, in hyperlipidemic rats. The animals fed either with normal fat diet or high fat diet were administered orally saffron (25, 50, and 100 mg/kg) or crocin (4.84, 9.69, and 19.38 mg/kg) in their respective groups for five consecutive days. Biochemical estimations of triglyceride (TG), total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), alkaline phosphatase (ALP), aspartate transaminase (AST), alanine aminotransferase (ALT), malondialdehyde (MDA), glutathione peroxidase enzyme activity (GSHPx), total glutathione (GSH), and oxidized glutathione (GSSG) in serum and superoxide dismutase (SOD), catalase (CAT), thiobarbituric acid reactive species (TBARS), ferric reducing/antioxidant power (FRAP), and total sulfhydryl (SH) groups in liver tissue homogenate were carried out. Both saffron and crocin were effective in decreasing the elevated levels of TG, TC, ALP, AST, ALT, MDA, GSHPx, GSH, and GSSG in serum and increasing SOD, CAT, FRAP, and SH values in liver tissue with reduction in TBARS. The saffron was found to be superior to crocin indicating the involvement of other potential constituents of saffron apart from crocin for its synergistic behavior of quenching the free radicals and ameliorating the damages of hyperlipidemia.

Recent Advances in Microbial Raw Starch Degrading Enzymes

Abstract: Raw starch degrading enzymes (RSDE) refer to enzymes that can directly degrade raw starch granules below the gelatinization temperature of starch. These promising enzymes can significantly reduce energy and simplify the process in starch industry. RSDE are ubiquitous and produced by plants, animals, and microorganisms. However, microbial sources are the most preferred one for large-scale production. During the past few decades, RSDE have been studied extensively. This paper reviews the recent development in the production, purification, properties, and application of microbial RSDE. This is the first review on microbial RSDE to date.

α-Amylase: An Ideal Representative of Thermostable Enzymes

Abstract: The conditions prevailing in the industrial applications in which enzymes are used are rather extreme, especially with respect to temperature and pH. Therefore, there is a continuing demand to improve the stability of enzymes and to meet the requirements set by specific applications. In this respect, thermostable enzymes have been proposed to be industrially relevant. In this review, α-amylase, a well-established representative of thermostable enzymes, providing an attractive model for the investigation of the structural basis of thermostability of proteins, has been discussed.

Production of acetone-butanol-ethanol (ABE) in direct fermentation of cassava by Clostridium saccharoperbutylacetonicum N1-4.

Abstract: In this work, acetone-butanol-ethanol (ABE) fermentation characteristics of cassava starch and cassava chips when using Clostridium saccharoperbutylacetonicum N1-4 was presented. The obtained results in batch mode using a 1-L fermenter showed that C. saccharoperbutylacetonicum N1-4 was a hyperamylolytic strain and capable of producing solvents efficiently from cassava starch and cassava chips, which was comparable to when glucose was used. Batch fermentation of cassava starch and cassava chips resulted in 21.0 and 19.4 g/L of total solvent as compared with 24.2 g/L of total solvent when using glucose. Solvent productivity in fermentation of cassava starch was from 42% to 63% higher than that obtained in fermentation using corn and sago starches in the same condition. In fermentation of cassava starch and cassava chips, maximum butanol concentration was 16.9 and 15.5 g/L, respectively. Solvent yield and butanol yield (based on potential glucose) was 0.33 and 0.41, respectively, for fermentation of cassava starch and 0.30 and 0.38, respectively for fermentation using cassava chips.

Pretreatment of Rice Straw by a Hot-Compressed Water Process for Enzymatic Hydrolysis

Abstract: Hot-compressed water (HCW) is among several cost-effective pretreatment processes of lignocellulosic biomass for enzymatic hydrolysis. The present work investigated the characteristics of HCW pretreatment of rice straw including sugar production and inhibitor formation in the liquid fraction and enzymatic hydrolysis of pretreated material. Pretreatment was carried out at a temperature ranging from 140 to 240 °C for 10 or 30 min. Soluble oligosaccharides were found to constitute almost all the components of total sugars in the liquid fraction. The maximal production of total glucose at 180 °C and below accounted for 4.4–4.9% of glucan in raw material. Total xylose production peaked at 180 °C, accounting for 43.3% of xylan in raw material for 10-min pretreatment and 29.8% for 30-min pretreatment. The production of acetic acid increased at higher temperatures and longer treatment time, indicating more significant disruption of lignocellulosic structure, and furfural production achieved the maximum (2.8 mg/ml) at 200 °C for both 10-min and 30-min processes. The glucose yield by enzymatic hydrolysis of pretreated rice straw was no less than 85% at 180 °C and above for 30-min pretreatment and at 200 °C and above for 10-min pretreatment. Considering sugar recovery, inhibitor formation, and process severity, it is recommended that a temperature of 180 °C for a time of 30 min can be the most efficient process for HCW pretreatment of rice straw.

Role of human liver microsomes in in vitro metabolism of drugs-a review.

Abstract: Drug metabolism studies are essential and necessary during the evaluation of drugs. This review discusses the in vitro human liver models to estimate the drug metabolic fates in vivo. Different approaches are provided and emphasis is placed on the potential of human liver microsomes for drug metabolism and inhibition studies. The methodology for these studies using human liver microsomes, applications of human liver microsomes, and the drugs studied by human liver microsomes are listed. Human liver microsomes represent a critical experimental model for the evaluation of drug metabolites with a high probability of clinical success.

Biogas Production from Anaerobic Co-digestion of Food Waste with Dairy Manure in a Two-Phase Digestion System

Abstract: Co-digestion of food waste and dairy manure in a two-phase digestion system was conducted in laboratory scale. Four influents of R0, R1, R2, and R3 were tested, which were made by mixing food waste with dairy manure at different ratios of 0:1, 1:1, 3:1, and 6:1, respectively. For each influent, three runs of experiments were performed with the same overall hydraulic retention time (HRT) of 13 days but different HRT for acidification (1, 2, and 3 days) and methanogenesis (12, 11, and 10 days) in two-phase digesters. The results showed that the gas production rate (GPR) of co-digestion of food waste with dairy manure was enhanced by 0.8–5.5 times as compared to the digestion with dairy manure alone. Appropriate HRT for acidification was mainly determined by the biodegradability of the substrate digested. Three-, 2-, and 1-day HRT for acidification were found to be optimal for the digestion of R0, R1, and R2/R3, respectively, when overall HRT of 13 days was used. The highest GPR of 3.97 L/L·day was achieved for R3(6:1) in Run 1 (1 + 12 days), therefore, the mixing ratio of 6:1 and HRT of 1 day for acidification were considered to be the optimal ones and thus recommended for co-digestion of food waste and dairy manure. There were close correlations between degradation of organic matters and GPR. The highest VS removal rate was achieved at the same HRT for acidification and mixing ratio of food waste and dairy manure as GPR in the co-digestion. The two-phase digestion system showed good stability, which was mainly attributed to the strong buffering capacity with two-phase system and the high alkalinity from dairy manure when co-digested with food waste.

Ball milling pretreatment of corn stover for enhancing the efficiency of enzymatic hydrolysis.

Abstract: Ethanol can be produced from lignocellulosic biomass with the usage of ball milling pretreatment followed by enzymatic hydrolysis and fermentation. The sugar yields from lignocellulosic feed stocks are critical parameters for ethanol production process. The research results from this paper indicated that the yields of glucose and xylose were improved by adding any of the following dilute chemical reagents: H2SO4, HCl, HNO3, CH3COOH, HCOOH, H3PO4, and NaOH, KOH, Ca(OH)2, NH3·H2O in the ball milling pretreatment of corn stover. The optimal enzymatic hydrolysis efficiencies were obtained under the conditions of ball milling in the alkali medium that was due to delignification. The data also demonstrated that ball milling pretreatment was a robust process. From the microscope image of ball milling-pretreated corn stover, it could be observed that the particle size of material was decreased and the fiber structure was more loosely organized. Meanwhile, the results indicate that the treatment effect of wet milling is better than that of dry milling. The optimum parameters for the milling process were ball speed of 350 r/min, solid/liquid ratio of 1:10, raw material particle size with 0.5 mm, and number of balls of 20 (steel ball, Φ = 10 mm), grinding for 30 min. In comparison with water milling process, alkaline milling treatment could increase the enzymatic hydrolysis efficiency of corn stover by 110%; and through the digestion process with the combination of xylanase and cellulase mixture, the hydrolysis efficiency could increase by 160%.

Enhanced biodegradation of hydrocarbons in soil by microbial biosurfactant, sophorolipid.

Abstract: Effectiveness of a microbial biosurfactant, sophorolipid, was evaluated in washing and biodegradation of model hydrocarbons and crude oil in soil. Thirty percent of 2-methylnaphthalene was effectively washed and solubilized with 10 g/L of sophorolipid with similar or higher efficiency than that of commercial surfactants. Addition of sophorolipid in soil increased biodegradation of model compounds: 2-methylnaphthalene (95% degradation in 2 days), hexadecane (97%, 6 days), and pristane (85%, 6 days). Also, effective biodegradation method of crude oil in soil was observed by the addition of sophorolipid, resulting in 80% biodegradation of saturates and 72% aromatics in 8 weeks. These results showed the potentials of the microbial biosurfactant, sophorolipid, as an effective surfactant for soil washing and as an in situ biodegradation enhancer.

Structure and Applications of a Rhamnolipid Surfactant Produced in Soybean Oil Waste

Abstract: Soybean oil soapstock was utilized as an alternative carbon source for the production of rhamnolipids by Pseudomonas aeruginosa LBI strain. The chemical composition and properties of the rhamnolipid mixture obtained were determined to define its potential applications. The chemical characterization of the rhamnolipid has revealed the presence of ten different homologues. The monorhamnolipid RhaC10C10 and the dirhamnolipid Rha2C10C10 were the main components of the mixture that showed predominance of 44% and 29%, respectively, after 144-h of cultivation. The biosurfactant was able to form stable emulsions with several hydrocarbons and showed excellent emulsification for soybean oil and chicken fat (100%). The rhamnolipid removed 67% of crude oil present in sand samples and presented antimicrobial activity against Bacillus cereus and Mucor miehei at 64 μg/mL and inhibition of Neurospora crassa, Staphylococcus aureus, and Micrococcus luteus at 256 μg/mL. The results demonstrated that the rhamnolipid produced in soybean oil soapstock can be useful in environmental and food industry applications.

Xylooligosaccharides Production from Alkali-Pretreated Sugarcane Bagasse Using Xylanases from Thermoascus aurantiacus

Abstract: Sugarcane bagasse hemicellulose was isolated in a one-step chemical extraction using hydrogen peroxide in alkaline media. The polysaccharide containing 80.9% xylose and small amounts of l-arabinose, 4-O-methyl-d-glucuronic acid and glucose, was hydrolyzed by crude enzymatic extracts from Thermoascus aurantiacus at 50 °C. Conditions of enzymatic hydrolysis leading to the best yields of xylose and xylooligosaccharides (DP 2-5) were investigated using substrate concentration in the range 0.5–3.5% (w/v), enzyme load 40–80 U/g of the substrate, and reaction time from 3 to 96 h, applying a 22 factorial design. The maximum conversion to xylooligosaccharides (37.1%) was obtained with 2.6% of substrate and xylanase load of 60 U/g. The predicted maximum yield of xylobiose by a polynomial model was 41.6%. Crude enzymatic extract of T. aurantiacus generate from sugarcane bagasse hemicellulose 39% of xylose, 59% of xylobiose, and 2% of other xylooligosaccharides.

Heterotrophic Culture of Chlorella protothecoides in Various Nitrogen Sources for Lipid Production

Abstract: The influences of urea, yeast extract, and nitrate as the nitrogen source on heterotrophic growth of four strains of Chlorella protothecoides were investigated in 9-day feed-batch cultures. Biomass dry weight concentration (DWC) and lipid yield (LY) of the four strains in all media were compared. The highest LY in 9 days was 654 mg/L/day by UTEX 255 in 2.4 g/L KNO(3) medium with a biomass DWC of 11.7 g/L and lipid content of 50.5%. Using green autotrophic seeds instead of yellow heterotrophic seeds improved the biomass DWC (13.1 vs. 11.7 g/L), LY (850 vs. 654 mg/L/day), and lipid to glucose consumption ratio (0.607 vs. 0.162). Moreover, 17.0 g/L DWC and 489 mg/L/day LY were obtained from the sequentially mixed-nitrogen medium, and the lipid to glucose consumption ratio was improved to 0.197 from 0.162 in 2.4 g/L nitrate medium and from 0.108 in 4.2 g/L yeast extract medium in the first batch.

Enhanced Enzymatic Hydrolysis of Lignocellulose by Optimizing Enzyme Complexes

Abstract: To enhance the conversion of the cellulose and hemicellulose, the corncob pretreated by aqueous ammonia soaking was hydrolyzed by enzyme complexes. The saturation limit for cellulase (Spezyme CP) was determined as 15 mg protein/g glucan (50 filter paper unit (FPU)/g glucan). The accessory enzymes (β-glucosidase, xylanase, and pectinase) were supplemented to hydrolyze cellobiose (cellulase-inhibiting product), hemicellulose, and pectin (the component covering the fiber surfaces), respectively. It was found that β-glucosidase (Novozyme 188) loading of 1.45 mg protein/g glucan [30 cellobiase units (CBU)/g glucan] was enough to eliminate the cellobiose inhibitor, and 2.9 mg protein/g glucan (60 CBU/g glucan) was the saturation limit. The supplementation of xylanase and pectinase can increase the conversion of cellulose and hemicellulose significantly. The yields of glucose and xylose enhanced with the increasing enzyme loading, but the increasing trend became low at high loading. Compared with xylanase, pectinase was more effective to promote the hydrolysis of cellulose and hemicellulose. The supplementation of pectinase with 0.12 mg protein/g glucan could increase the yields of glucose and xylose by 7.5% and 29.3%, respectively.

Probiotic bile salt hydrolase: current developments and perspectives.

Abstract: Probiotic has modernized the current dietetic sense with novel therapeutic and nutritional benefits to the consumers. The presence of bile salt hydrolase (BSH) in probiotics renders them more tolerant to bile salts, which also helps to reduce the blood cholesterol level of the host. This review focuses on the occurrence of bile salt hydrolase among probiotics and its characterization, importance, applications, and genetics involved with recent updates. Research on bile salt hydrolase is still in its infancy. The current perspective reveals a huge market potential of probiotics with bile salt hydrolase. Intensive research in this field is desired to resolve some of the lacunae.

Antibacterial activities of crude extract of Aloe barbadensis to clinically isolated bacterial pathogens.

Abstract: The antibacterial activity of Aloe barbadensis was tested on clinically isolated bacterial pathogens i.e. Enterococcus bovis, Staphylococcus aureus, Escherichia coli, Proteus vulgaris, Proteus mirabilis, Pseudomonas aeruginosa, Morganella morganii, and Klebsiella pneumoniae causing infection in human being. Ethanolic and aqueous extracts were used for the antibacterial effect, which was measured by the appearance of zone of inhibition. Relatively higher MIC concentrations were obtained for gram negative bacteria E. coli and K. pneumoniae, with ethanol extract; however, no inhibitory effect was noted for aqueous extract. Ethanolic extract possesses great inhibitory activity for gram positive bacteria, E. bovis followed by S. aureus. Among gram negative bacteria, highest inhibitory effect was observed with P. aeruginosa, followed by M. morganii, P. mirabilis, and P. vulgaris, which was significant (p < 0.01) than E. coli and K. pneumoniae. Antimicrobial activity tests of crude extract of A. barbadensis were carried out to validate the use of traditional medicinal herbal and results of this study tend to give credence to the common use of A. barbadensis gel and leaf.

Bioconversion of Kraft paper mill sludges to ethanol by SSF and SSCF.

Abstract: Paper mill sludge is a solid waste material composed of pulp residues and ash generated from pulping and paper making processes. The carbohydrate portion of the sludge has chemical and physical characteristics similar to pulp. Because of its high carbohydrate content and well-dispersed structure, the sludges can be biologically converted to value-added products without pretreatment. In this study, two different types of paper mill sludges, primary sludge and recycle sludge, were evaluated as a feedstock for bioconversion to ethanol. The sludges were first subjected to enzymatic conversion to sugars by commercial cellulase enzymes. The enzymatic conversion was inefficient because of interference by ash in the sludges with the enzymatic reaction. The main cause was that the pH level is dictated by CaCO3 in ash, which is two units higher than the pH optimum of cellulase. To alleviate this problem, simultaneous saccharification and cofermentation (SSCF) using cellulase (Spezyme CP) and recombinant Escherichia coli (ATCC-55124), and simultaneous saccharification and fermentation (SSF) using cellulase and Saccharomyces cerevisiae (ATCC-200062) were applied to the sludges without any pretreatment. Ethanol yields of 75–81% of the theoretical maximum were obtained from the SSCF on the basis of total carbohydrates. The yield from the SSF was also found to be in the range of 74–80% on the basis of glucan. The SSCF and SSF proceeded under stable condition with the pH staying near 5.0, close to the optimum for cellulase. Decrease of pH occurred due to carbonic acid and other organic acids formed during fermentation. The ash was partially neutralized by the acids produced from the SSCF and SSF and acted as a buffer to stabilize the pH during fermentation. When the SSF and SSCF were operated in fed-batch mode, the ethanol concentration in the broth increased from 25.5 and 32.6 g/L (single feed) to 45 and 42 g/L, respectively. The ethanol concentration was limited by the tolerance of the microorganism in the case of SSCF. The ethanol yield in fed-batch operation decreased to 68% for SSCF and 70% for SSF. The high-solids condition in the bioreactor appears to create adverse effects on the cellulase reaction.

Microbial fed-batch production of 1,3-propanediol using raw glycerol with suspended and immobilized Klebsiella pneumoniae.

Abstract: The production of 1,3-propanediol (1,3-PD) was investigated with Klebsiella pneumoniae DSM 4799 using raw glycerol without purification obtained from a biodiesel production process. Fed-batch cultures with suspended cells revealed that 1,3-PD production was more effective when utilizing raw glycerol than pure glycerol (productivity after 47 h of fermentation, 0.84 g L−1 h−1 versus 1.51 g L−1 h−1 with pure and raw glycerol, respectively). In addition, more than 80 g/L of 1,3-PD was produced using raw glycerol; this is the highest 1,3-PD concentration reported thus far for K. pneumoniae using raw glycerol. Repeated fed-batch fermentation with cell immobilization in a fixed-bed reactor was performed to enhance 1,3-PD production. Production of 1,3-PD increased with the cycle number (1.06 g L−1 h−1 versus 1.61 g L−1 h−1 at the first and fourth cycle, respectively) due to successful cell immobilization. During 46 cycles of fed-batch fermentation taking place over 1,460 h, a stable and reproducible 1,3-PD production performance was observed with both pure and raw glycerol. Based on our results, repeated fed batch with immobilized cells is an efficient fermentor configuration, and raw glycerol can be utilized to produce 1,3-PD without inhibitory effects caused by accumulated impurities.

Influence of Extruder Temperature and Screw Speed on Pretreatment of Corn Stover while Varying Enzymes and Their Ratios

Abstract: Pretreatment is being the first and most expensive step, it has pervasive impacts on all other steps in overall conversion process. There are several pretreatment methods using physical, chemical, and biological principles which are under various stages of investigation. Extrusion can be used as one of the physical pretreatment methods towards biofuel production. The objective of this study was to evaluate the effect of barrel temperature and screw speed on sugar recovery from corn stover, to select a suitable enzyme combination and its ratio. Corn stover was pretreated in a single screw extruder with five screw speeds (25, 50, 75, 100, and 125 rpm) and five barrel temperatures (25, 50, 75, 100, and 125 °C). In order to select a suitable enzyme combination and ratio, different levels of cellulase and β-glucosidase, multienzyme complex and β-glucosidase were used during saccharification of pretreated corn stover. From the statistical analysis, it was found that screw speed and temperature had a significant effect on sugar recovery from corn stover. Higher glucose, xylose, and combined sugar recovery of 75, 49, and 61%, respectively, were recorded at 75 rpm and 125 °C. This pretreatment condition resulted in 2.0, 1.7, and 2.0 times higher than the control sample using 1:4 cellulase and β-glucosidase combination.

A new strategy for lipid production by mix cultivation of Spirulina platensis and Rhodotorula glutinis.

Abstract: Mix cultivation of microalgae (Spirulina platensis) and yeast (Rhodotorula glutinis) for lipid production was studied. Mixing cultivation of the two microorganisms significantly increased the accumulation of total biomass and total lipid yield. Dissolved oxygen and medium components in the mixed fermentation medium were analyzed. Mix cultivation in monosodium glutamate wastewater was further studied. Result indicated 1,600 mg/L of biomass was obtained and 73% of COD were removed.