Showing papers in "Applied Biochemistry and Biotechnology in 1998"
TL;DR: In this paper, the authors used lime (calcium hydroxide) as a pretreatment agent to enhance the enzymatic digestibility of two common crop residues: bagasse and wheat straw.
Abstract: Lime (calcium hydroxide) was used as a pretreatment agent to enhance the enzymatic digestibility of two common crop residues: bagasse and wheat straw. A systematic study of pretreatment conditions suggested that for short pretreatment times (1–3 h), high temperatures (85-135°C) were required to achieve high sugar yields, whereas for long pretreatment times (e.g., 24 h), low temperatures (50–65°C) were effective. The recommended lime loading is 0.1 g Ca(OH)2/g dry biomass. Water loading had little effect on the digestibility. Under the recommended conditions, the 3-d reducing sugar yield of the pretreated bagasse increased from 153 to 659 mg Eq glucose/g dry biomass, and that of the pretreated wheat straw increased from 65 to 650 mg Eq glucose/g dry biomass. A material balance study on bagasse showed that the biomass yield after lime pretreatment is 93.6%. No glucan or xylan was removed from bagasse by the pretreatment, whereas 14% of lignin became solubilized. A lime recovery study showed that 86% of added calcium was removed from the pretreated bagasse by ten washings and could be recovered by carbonating the wash water with CO2 at pH 9.5.
253 citations
TL;DR: In this article, the pretreatment of softwood with sulfuric acid impregnation in the production of ethanol, based on enzymatic hydrolysis, has been investigated.
Abstract: The pretreatment of softwood with sulfuric acid impregnation in the production of ethanol, based on enzymatic hydrolysis, has been investigated. The parameters investigated were: H2SO4 concentration (0.5–4.4% w/w liquid), temperature (180–240°C), and residence time (1-20 minutes). The combined severity (log Ro-pH) was used to combine the parameters into a single reaction ordinate. The highest yields of fermentable sugars, i.e., glucose and mannose, were obtained at a combined severity of 3. At this severity, however, the fermentability declined and the ethanol yield decreased. In a comparison with previous results, SO2 impregnation was found to be preferable, since it resulted in approximately the same sugar yields, but better fermentability.
186 citations
TL;DR: In this paper, the pH level of the sugarcane bagasse hemicellulose hydrolysate was changed by changing the initial pH level through the combination of different bases and acids with or without the subsequent addition of activated charcoal.
Abstract: In order to remove or reduce the concentrations of toxic substances present in the sugarcane bagasse hemicellulose hydrolysate for xylose-to-xylitol bioconversion, the hydrolysate was pretreated by changing the initial pH level through the combination of different bases and acids with or without the subsequent addition of activated charcoal. Attention was given to the influence of the fermentation time as well.
141 citations
TL;DR: In this paper, a 2-L, 304 SS, Parr reactor with three turbine propeller agitators and a Proportional-Integral-Derivative (PID) controller was used for cooking corn fiber at temperatures ranging from 200 to 260°C.
Abstract: The pretreatment of corn fiber using liquid water at temperatures between 220 and 260°C enhances enzymatic hydrolysis. This paper describes the laboratory reactor system currently in use for cooking of corn fiber at temperatures ranging from 200 to 260°C. The corn fiber at approx 4.4% solid/liquid slurry was treated in a 2-L, 304 SS, Parr reactor with three turbine propeller agitators and a Proportional-Integral-Derivative (PID), controller that controlled temperature within ±1°C. Heat-up times to the final temperatures of 220, 240, or 260°C were achieved in 50 to 60 min. Hold time at the final temperature was less than 10 s. A serpentine cooling coil, through which tap water was circulated at the completion of the run, cooled the reactor’s contents to 180°C within 2 min after the maximum temperature was attained. Ports in the reactor’s head plate facilitated sampling of the slurry and monitoring the pH. A continuous pH monitoring system was developed to help observe trends in pH during pretreatment and to assist in the development of a base (2.0M KOH) addition profile to help keep the pH within the range of 5.0 to 7.0. Enzymatic hydrolysis gave 33 to 84% conversion of cellulose in the pretreated fiber to glucose compared to 17% for untreated fiber.
127 citations
TL;DR: The data support the emergence in E.coli of a novel succinic acid:acetic acid:ethanol fermentation pathway, and the mutant strain named AFP111, fermented glucose more slowly than did its wild-type ancestor, strain W1485, and generated a very different spectrum of products.
Abstract: Escherichia coli strain NZN111, which is unable to grow fermentatively because of insertional inactivation of the genes encoding pyruvate: formate lyase and the fermentative lactate dehydrogenase, gave rise spontaneously to a chromosomal mutation that restored its ability to ferment glucose. The mutant strain, named AFP111, fermented glucose more slowly than did its wild-type ancestor, strain W1485, and generated a very different spectrum of products. AFP111 produced succinic acid, acetic acid, and ethanol in proportions of approx 2:1:1. Calculations of carbon and electron balances accounted fully for the observed products; 1 mol of glucose was converted to 1 mol of succinic acid and 0.5 mol each of acetic acid and ethanol. The data support the emergence in E. coli of a novel succinic acid:acetic acid:ethanol fermentation pathway.
126 citations
TL;DR: Results reveal that at least one synthetic mixture utilizing enzymes from three different organisms delivers performance competitive with that of a "native" (i.e., co-evolved) ternary system drawn exclusively from T. reesei.
Abstract: The saccharification of microcrystalline cellulose by reconstituted ternary mixtures of purified cellulases (one endoglucanase and two cello-biohydrolases) has been studied over the entire range of mixture compositions. Ternary plots are used to compare the performance of five synthetic mixtures drawn from the cellulase systems of Acidothermus cel-lulolyticus, Trichoderma reesei, Thermomonospora fusca, and Thermotoga nea-politana. Results reveal that at least one synthetic mixture utilizing enzymes from three different organisms delivers performance competitive with that of a “native” (i.e., co-evolved) ternary system drawn exclusively from T. reesei. This heterologous system, consisting of the endoglucanase El from A. cellulolyticus and the exoglucanases CBHI from T. ressei and E3 from T. fusca, is forgiving from the system-design point of view, in that it delivers high saccharification rates over a wide range of mixture compositions.
114 citations
TL;DR: In this paper, Douglas fir chips were soaked in 0.4% sulfuric acid solution, then pretreated with steam at 200 - 230°C for 1 - 5 min. After pretreatment, 90 - 95% of the hemicellulose and as much as 20% of cellulose was solubilized in water, and 90% of remaining cellulose can be hydrolyzed to glucose by cellulase enzyme.
Abstract: Selective thinning of forests in the western United States will generate a large, sustainable quantity of softwood residues that can be an attractive feedstock for fuel ethanol production. The major species available from thinning of forests in northern California and the eastern Rocky Mountains include white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii), and Ponderosa pine (Pinus ponderosa). Douglas fir chips were soaked in 0.4% sulfuric acid solution, then pretreated with steam at 200 – 230°C for 1 – 5 min. After pretreatment, 90 – 95% of the hemicellulose and as much as 20% of the cellulose was solubilized in water, and 90% of the remaining cellulose can be hydrolyzed to glucose by cellulase enzyme. The prehydrolysates, at as high as 10% total solid concentration, can be readily fermented by the unadapted yeastSaccharomyces cerevisiae D5A.
113 citations
TL;DR: In this paper, a continuous pH-monitoring system was developed to help characterize the trends in pH during pretreatment and to assist in the development of a base (2.0 M KOH) addition profile to help keep the pH within a specified range in order to reduce any catalytic degradation and the formation of any monosac-charide degradation products during pre-treatment.
Abstract: Yellow poplar wood sawdust consists of 41% cellulose and 19% hemicellulose. The goal of pressure cooking this material in water is to hydrate the more chemically resistive regions of cellulose in order to enhance enzymatic conversion to glucose. Pretreatment can generate organic acids through acid-catalyzed degradation of monosaccharides formed because of acids released from the biomass material or the inherent acidity of the water at temperatures above 160°C The resulting acids will further promote the acid-catalyzed degradation of monomers that cause both a reduction in the yield and the formation of fermentation inhibitors such as hydroxymethyl furfural and furfural. A continuous pH-monitoring system was developed to help characterize the trends in pH during pretreatment and to assist in the development of a base (2.0 M KOH) addition profile to help keep the pH within a specified range in order to reduce any catalytic degradation and the formation of any monosac-charide degradation products during pretreatment. The results of this work are discussed.
107 citations
TL;DR: Results were obtained that indicate the complement-independent cytotoxicity of anti-DNA autoantibodies isolated from blood of patients with SLE and chronic lymphocytic leukemia and a new mechanism of formation of DNA-specific catalytic Abs has been proposed based on the increased crossreactivity of polyclonal DNA-abzymes to DNA-depleted nuclear matrix proteins.
Abstract: DNA-hydrolyzing activity of IgG autoantibodies from sera of patients with various types of lymphoproliferative diseases was investigated. The association of DNA-hydrolyzing activity with the antibody (Ab) fraction has been proved by newly developed affinity-capture assay. Study of abzyme incidence in blood tumors and systemic lupus erythematosis (SLE) revealed linkage of anti-DNA Ab catalysts to mature B-cell tumors, and increased probability of DNA-abzymes formation on the background of autoimmune manifestations. These data suggest possible similarity between mechanisms of abzyme formation in SLE and B-cell lymphomas. A new mechanism of formation of DNA-specific catalytic Abs has been proposed based on the increased crossreactivity of polyclonal DNA-abzymes to DNA-depleted nuclear matrix proteins. The possibility of the abzyme production as Ab to the energetically destabilized ground state of the antigen has been discussed. Preliminary results were obtained that indicate the complement-independent cytotoxicity of anti-DNA autoantibodies isolated from blood of patients with SLE and chronic lymphocytic leukemia.
101 citations
TL;DR: The results of these experiments indicated that, with the use of different types of food wastes as the C source, different polyhydroxyal-kanoate copolymers could be produced with distinct polymer properties.
Abstract: The usage of plastics in packaging and disposable products, and the generation of plastic waste, have been increasing drastically. Broader usage of biodegradable plastics in packaging and disposable products as a solution to environmental problems would heavily depend on further reduction of costs and the discovery of novel biodegradable plastics with improved properties. In the authors’ laboratories, various carbohydrates in the growth media, including sucrose, lactic acid, butyric acid, valeric acid, and various combinations of butyric and valeric acids, were utilized as the carbon (c) sources for the production of bioplastics by Alcaligenes eutrophus. As the first step in pursuit of eventual usage of industrial food wastewater as nutrients for microorganisms to synthesize bioplastics, the authors investigated the usage of malt wastes from a beer brewery plant as the C sources for the production of bioplastics by microorganisms. Specific polymer production yield by A. Latus DSM 1124 increased to 70% polymer/cell (g/g) and 32g/L cell dry wt, using malt wastes as the C source. The results of these experiments indicated that, with the use of different types of food wastes as the C source, different polyhydroxyal-kanoate copolymers could be produced with distinct polymer properties.
74 citations
TL;DR: Several promising pretreatment and enzymatic processes for conversion of corn fiber cellulose, hemicellulose, and remaining starch to fermentable sugars were evaluated in this paper.
Abstract: Corn fiber, which consists of about 20% starch, 14% cellulose, and 35% hemicellulose, has the potential to serve as a low cost feedstock for production of fuel ethanol. Currently, the use of corn fiber to produce fuel ethanol faces significant technical and economic challenges. Its success depends largely on the development of environmentally friendly pretreatment procedures, highly effective enzyme systems for conversion of pretreated corn fiber to fermentable sugars, and efficient microorganisms to convert multiple sugars to ethanol. Several promising pretreatment and enzymatic processes for conversion of corn fiber cellulose, hemicellulose, and remaining starch to fermentable sugars were evaluated. These hydrolyzates were then examined for ethanol production in bioreactors, using genetically modified bacteria and yeast. Several novel enzymes were also developed for use in pretreated corn fiber saccharification.
TL;DR: It is concluded that the inhibitory effect of acetic acid on xylose utilization in the SSCF biomass-to-ethanol process will be partially ameliorated because of the simultaneous saccharification of the cellulose.
Abstract: In the production of ethanol from lignocellulosic biomass, the hydrolysis of the acetylated pentosans in hemicellulose during pretreatment produces acetic acid in the prehydrolysate. The National Renewable Energy Laboratory (NREL) is currently investigating a simultaneous saccharification and cofermentation (SSCF) process that uses a proprietary metabolically engineered strain ofZymomonas mobilis that can coferment glucose and xylose. Acetic acid toxicity represents a major limitation to bioconversion, and cost-effective means of reducing the inhibitory effects of acetic acid represent an opportunity for significant increased productivity and reduced cost of producing fermentation fuel ethanol from biomass. In this study, the fermentation performance of recombinant Z.mobilis 39676:pZB4L, using a synthetic hardwood prehydrolysate containing 1% (w/v) yeast extract, 0.2% KH2PO4, 4% (w/v) xylose, and 0.8% (w/v) glucose, with varying amounts of acetic acid was examine. To minimize the concentration of the inhibitory undissociated form of acetic acid, the pH was controlled at 6.0. The final cell mass concentration decreased linearly with increasing level of acetic acid over the range 0-0.75% (w/v), with a 50% reduction at about 0.5% (w/v) acetic acid. The conversion efficiency was relatively unaffected, decreasing from 98 to 92%. In the absence of acetic acid, batch fermentations were complete at 24 h. In a batch fermentation with 0.75% (w/v) acetic acid, about two-thirds of the xylose was not metabolized after 48 h. In batch fermentations with 0.75% (w/v) acetic acid, increasing the initial glucose concentration did not have an enhancing effect on the rate of xylose fermentation. However, nearly complete xylose fermentation was achieved in 48 h when the bioreactor was fed glucose. In the fed-batch system, the rate of glucose feeding (0.5 g/h) was designed to simulate the rate of cellulolytic digestion that had been observed in a modeled SSCF process with recombinant Zymomonas. In the absence of acetic acid, this rate of glucose feeding did not inhibit xylose utilization. It is concluded that the inhibitory effect of acetic acid on xylose utilization in the SSCF biomass-to-ethanol process will be partially ameliorated because of the simultaneous saccharification of the cellulose.
TL;DR: This mini-review describes the most significant upstream parameters on xylitol production by biotechnological process, which have several economic advantages in comparison with the conventional process based on the chemical reduction of xylose.
Abstract: Xylitol is a sweetener with important technological properties like anticariogenicity, low caloric value, and negative dissolution heat Because it can be used successfully in food formulations and pharmaceutical industries, its production is in great demand Xylitol can be obtained by microbiological process, since many yeasts and filamentous fungi synthesize the xylose reductase enzyme, which catalyses the xylose reduction into xylitol as the first step in the xylose metabolism The xylitol production by biotechnological means has several economic advantages in comparison with the conventional process based on the chemical reduction of xylose The efficiency and the productivity of this fermentation chiefly depends upon the microorganism and the process conditions employed In this mini-review, the most significant upstream parameters on xylitol production by biotechnological process are described
TL;DR: Possibility of fermentation routes from carbohydrates to acrylic acid and novel approaches involving recombinant microorganisms are illustrated, which would open a new market for renewable resources within the chemical industry.
Abstract: The quantitative conversion of lactic acid to acrylic acid would open a new market for renewable resources within the chemical industry. This paper focuses on the theoretical ways of producing acrylics out of renewable resources. It summarizes possible fermentation routes from carbohydrates to acrylic acid and reviews former research activities in this area. It also illustrates novel approaches involving recombinant microorganisms.
TL;DR: Succinic acid was produced efficiently from fumaric acid by a recombinantE.
Abstract: Succinic acid was produced efficiently from fumaric acid by a recombinant E. coli strain DH5α/pGC1002 containing multicopy fumarate reductase genes. The effects of initial fumaric acid and glucose concentration on the production of succinic acid were investigated. Succinic acid reached 41 to over 60 g/L in 48.5 h starting with 50 to 64 g/L fumaric acid. Significant substrate inhibition was observed at initial fumaric acid concentration of 90 g/L. l-Malic acid became the major fermentation product under these conditions. Provision of glucose (5–30 g/L) to the fermentation medium stimulated the initial succinic acid production rate over two folds.
TL;DR: It is shown by different methods that IgG from the milk of normal females possesses both DNase and RNase activities, and these findings speak in favor of the generation of cat alytic Abs by the immune system of healthy mothers.
Abstract: Various catalytically active antibodies (Abs), or abzymes, have been detected recently in the sera of patients with autoimmune pathologies, in whom their presence is probably associated with autoimmunization. Normal humans are generally not considered to have abzymes, since no obvious immunizing factors are present. Here is shown by different methods that IgG from the milk of normal females possesses both DNase and RNase activities. The activities were also present in the IgG F(ab′)2 and Fab fragments. Affinity modification of IgG by the chemically reactive derivative of an oligonucleotide led to preferential modification of the L chain of IgG. After separation of the subunits by sodium dodecyl sulfate electrophoresis in a gel containing DNA, an in-gel assay showed DNase activity in the L chain. The L chain separated by affinity chromatography on DNA-cellulose was catalytically active. These findings speak in favor of the generation of cat alytic Abs by the immune system of healthy mothers. It is known that the treatment of adults with DNases and RNases offers protection from viral and bacterial diseases. Since breast milk protects the infants from infec tions until the immune system is developed, this raises the possibility that catalytic Abs like nucleases, may possess a protective role.
TL;DR: A new medium based on the hydrolysate of gruel, a cheap and abundant byproduct of semolina factories, supporting growth and δ-endotoxin synthesis, was formulated, supported by the effect of some principal nutrients was deeply investigated.
Abstract: Nutritional requirements of a strain ofBacillus thuringiensis (Bt) subsp.kurstaki were elucidated for δ-endotoxin production. The effect of some principal nutrients was deeply investigated, showing several nutritional and metabolite limitations in Bt growth and δ-endotoxin synthesis. This led us to formulate a new medium based on the hydrolysate of gruel, a cheap and abundant byproduct of semolina factories, supporting growth and δ-endotoxin synthesis. After hydrolysis of gruel by α-amylase, followed by proteolysis using alcalase, the resultant soluble material substituted glucose very well for Bt δ-endotoxin production. Indeed, 15 g/L total sugars coming from that hydrolysate, supplemented by 5.4 g/L ammonium sulfate as nitrogen source and either 5 g/L yeast extract or 3 g/L peptone from casein or 3 g/L casaminoacids or 0.25 g/L cysteine or aspartic acid, were the principal components of this new medium in which almost 1 g/L of δ-endotoxin in 4.5 g/L total dry biomass was produced.
TL;DR: Neoplastic tissues, marked by Cra Iso 1, showed a higher intensity of staining than normal ones, in comparison with Canavalia ensiformis lectin, Concanavalin A, conjugated to peroxidase (Con A-Per).
Abstract: The phenomenon of altered carbohydrates in transformed cell surfaces has been studied through histochemical techniques using lectins. Specific binding patterns to normal and transformed mammary tissues were evaluated by Isoform 1 from Cratylia mollis lectin (Cra Iso 1). Protocols using a direct method, incubation of Cra Iso I conjugated to peroxidase (Cra Iso 1-Per) with mammary tissues, followed by diaminobenzidine and hydrogen peroxidase interaction, were performed. Neoplastic tissues, marked by Cra Iso 1, showed a higher intensity of staining than normal ones, in comparison with Canavalia ensiformis lectin, Concanavalin A (Con A), conjugated to peroxidase (Con A-Per). The assay with Cra Iso 1 also indicated a possible utilization of this lectin to characterize normal and transformed mammary cells.
TL;DR: Batch fermentations were used to study the effect of different glycerol concentrations and pH conditions on growth of recombinantPichia pastoris, and there were no differences between Mut+ and Mut- strains during cell growth on Glycerol.
Abstract: Batch fermentations were used to study the effect of different glycerol concentrations and pH conditions on growth of recombinantPichia pastoris. Two strains ofP. pastoris were used: a wild-type in methanol utilization (Mut+) and a mutant defective in methanol utilization (Mut-). Under constant pH conditions of 5.0, glycerol concentrations up to 12% were efficiently utilized. Cell yield (Yx/s) of about 0.8 and a final cell density of about 95 g/L (dry cell) were achieved. However, there were significant differences (probability [Pr]> F 0.0351) in specific growth rates between the initial glycerol concentrations of 2, 7, and 12%. When fermentations were conducted without pH control, growth continued until the pH had decreased to about 2.5. Growth stopped at pH 2.2 with uncontrolled pH, and residual glycerol concentrations were greater than 2%. As a result, Yx/s decreased to about 0.3. There were no differences between Mut+ and Mut- strains during cell growth on glycerol.
TL;DR: The amount of fresh water used and the amount of waste water thereby produced in the production of fuel ethanol from softwood, can be reduced to a large extent by recycling of either the stillage stream or part of the liquid stream from the fermenter.
Abstract: In ethanol production from lignocellulose by enzymatic hydrolysis and fermentation, it is desirable to minimize addition of fresh-water and waste-water streams, which leads to an accumulation of substances in the process. This study shows that the amount of fresh water used and the amount of waste water thereby produced in the production of fuel ethanol from softwood, can be reduced to a large extent by recycling of either the stillage stream or part of the liquid stream from the fermenter. A reduction in fresh-water demand of more than 50%, from 3 kg/kg dry raw material to 1.5 kg/kg dry raw material was obtained without any negative effects on either hydrolysis or fermentation. A further decrease in the amount of fresh water, to one-fourth of what was used without recycling of process streams, resulted in a considerable decrease in the ethanol productivity and a slight decrease in the ethanol yield.
TL;DR: In this article, the authors used an alkali to extract a fraction of the lignin from the pretreated material to increase the accessibility of the cellulose to enzymatic attack, and thus improve overall economics of the process.
Abstract: A process for converting lignocellulosic biomass to ethanol hydrolyzes the hemicellulosic fraction to soluble sugars (i.e., pretreatment), followed by acid- or enzyme-catalyzed hydrolysis of the cellulosic fraction. Enzymatic hydrolysis may be improved by using an alkali to extract a fraction of the lignin from the pretreated material. The removal of the lignin may increase the accessibility of the cellulose to enzymatic attack, and thus improve overall economics of the process, if the alkali-treated material can still be effectively converted to ethanol.
TL;DR: The petroporphyrin-rich fractions and asphaltenes from a crude oil rich in heavy metals were fractionated and partially characterized, and only the CPO-mediated reactions were effective in eliminating the Soret peak in both aqueous and organic solvent systems.
Abstract: Asphaltenes from a crude oil rich in heavy metals (Castilla crude oil) were fractionated and partially characterized. Biocatalytic modifications of these fractionated asphaltenes by three different hemoproteins: chloro-peroxidase (CPO), cytochrome C peroxidase (Cit-C), and lignin peroxidase (LPO) were evaluated in both aqueous buffer and organic solvents. The reactions were carried out in aqueous buffers, ternary systems of toluene: isopropanol: water, and aqueous-miscible organic solvent solutions with petroporphyrins as substrate. The petroporphyrins were more soluble in the ternary systems and aqueous miscible-organic solvent systems than in the aqueous buffer systems. However, only the CPO-mediated reactions were effective in eliminating the Soret peak in both aqueous and organic solvent systems. The effects of CPO-mediated reactions on the release of the metals complexed with the porphyrins and asphaltenes were also determined. Chloroperoxidase was able to alter components in the heavy fractions of petroleum and remove 53 and 27% of total heavy metals (Ni and V, respectively) from petroporphyrin-rich fractions and asphaltenes.
TL;DR: The NSSF process has improved the enzymatic reaction in the SSF to the extent that it reduces the overall enzyme requirement by 30-40%.
Abstract: The enzymatic reaction in the simultaneous saccharification and fermentation (SSF) is operated at a temperature much lower than its optimum level. This forces the enzyme activity to be far below its potential, consequently raising the enzyme requirement. To alleviate this problem, a nonisothermal simultaneous saccharification and fermentation process (NSSF) was investigated. The NSSF is devised so that saccharification and fermentation occur simultaneously, yet in two separate reactors that are maintained at different temperatures. Lignocellulosic biomass is retained inside a column reactor and hydrolyzed at the optimum temperature for the enzymatic reaction (50°C). The effluent from the column reactor is recirculated through a fermenter, which runs at its optimum temperature (20-30°C). The cellulase enzyme activity is increased by a factor of 2-3 when the hydrolysis temperature is raised from 30 to 50°C. The NSSF process has improved the enzymatic reaction in the SSF to the extent that it reduces the overall enzyme requirement by 30-40%. The effect of temperature on β-glucosidase activity was the most significant among the individual cellulase compounds. Both ethanol yield and productivity in the NSSF are substantially higher than those in the SSF at the enzyme loading of 5 IFPU/g glucan. With 10 IFPU/g glucan, improvement in productivity was more discernible for the NSSF. The terminal yield attainable in 4 d with the SSF was reachable in 40 h with the NSSF.
TL;DR: Immobilization with a highly concentrated enzyme solution was advantageous for both the immobilized enzyme activity and activity recovery, indicating the inactivation of enzymes by their reaction with uncoupled aldehyde groups of carriers.
Abstract: Immobilization of a protease, Flavourzyme, by covalent binding on various carriers was investigated. Lewatit R258-K, activated with glutaraldehyde, was selected among the tested carriers, because of the highest immobilized enzyme activity. The optimization of activation and immobilization conditions was performed to obtain high recovery yield. The activity recovery decreased with increasing carrier loading over an optimal value, indicating the inactivation of enzymes by their reaction with uncoupled aldehyde groups of carriers. The buffer concentrations for carrier activation and enzyme immobilization were optimally selected as 500 and 50 mM, respectively. With increasing enzyme loading, the immobilized enzyme activity increased, but activity recovery decreased. Immobilization with a highly concentrated enzyme solution was advantageous for both the immobilized enzyme activity and activity recovery. Consequently, the optimum enzyme and carrier loadings for the immobilization of Flavourzyme were determined as 1.8 mg enzyme/mL and 0.6 g resin/mL, respectively.
TL;DR: Evidence that protein kinase activity is an intrin sic property of secretory immunoglobulin A from milk of healthy human mothers is presented and the likelihood that catalytic Abs are generated by the immune system of healthy mothers is suggested.
Abstract: This article presents evidence that protein kinase activity is an intrin sic property of secretory immunoglobulin A (sIgA) from milk of healthy human mothers. Polyclonal sIgA was purified by sequential chromatog raphy on protein A-Sepharose, DEAE-cellulose, and gel filtration on Toyopearl HW-55 and Sepharose 4B columns. Its purity was established by one-and two-dimensional SDS-PAGE. The protein kinase activity was inhibited by specific antibodies (Abs) against sIgA, and was stable to acidic and alkaline conditions. Catalytic sIgA showed optimal reaction conditions (pH and MgCl2 concentration) and substrate specificity dif ferent from those of known protein kinases; i.e., sIgA phosphorylated the serine residues of various milk proteins in the presence of different γ-[32P]nucleoside-and deoxynucleoside-5’-triphosphates. The homoge neous Fab fragment of sIgA also showed kinase activity. An ATP-binding activity of fractions of sIgA was demonstrated by affinity chromatog raphy on ATP-Sepharose and by covalent binding of an affinity analog of ATP; this activity was mediated by the L chain of sIgA. The authors believe these observations are the first example of the catalytic activity of IgA Abs and of natural catalytic Abs with synthetic activity. In addition, the findings suggest the likelihood that catalytic Abs are generated by the immune system of healthy mothers.
TL;DR: Electro-spray bioreactors did not prove to be advantageous for the IGTS8 desulfurization system, but may prove advantageous for systems that do not produce surface-active bioagents, in addition to being mass-transport limited.
Abstract: Biological removal of organic sulfur from petroleum feedstocks offers an attractive alternative to conventional thermochemical treatment, because of the mild operating conditions afforded by the biocatalyst. In order for biodesulfurization to realize commercial success, reactors must be designed that allow for sufficient liquid-liquid and gas-liquid mass transfer, while simultaneously reducing operating costs. Electro-spray bioreactors were investigated for use as desulfurization reactors because of their reported operational cost savings relative to mechanically agitated reactors. Unlike batch-stirred reactors, which mix the biocatalystcontaining aqueous phase with the organic feedstock by imparting momentum to the entire bulk solution, electro-spray reactors have the potential for tremendous cost savings, creating an emulsion <5 (μm in diameter, at a cost of only 3 W/L. Power law relationships indicate that mechanically stirred reactors would require 100-1000-fold more energy to create such a fine emulsion, but these relationships generally do not account for the effect of endogenously produced surfactant in the system. Here, the rates dibenzothiophene (DBT) oxidation to 2-hydroxybiphenyl (2-HBP) in hexadecane, byRhodococcus sp IGTS8 are compared in the two reactor systems. Desulfurization rates ranged from 1.0 to 5.0 mg 2-HBP/(dry g cells · h), independent of the reactor employed. The batch-stirred reactor was capable of forming a very fine emulsion in the presence of the biocatalyst IGTS8, similar to that formed in the emulsion phase contactor (EPTM), presumably because the biocatalyst produces its own surfactant. Although EPC did not prove to be advantageous for the IGTS8 desulfurization system, it may prove advantageous for systems that do not produce surface-active bioagents, in addition to being mass-transport limited.
TL;DR: The effect of the addition of different concentrations of Tween-80 and three different zeolite-like products on enzymatic hydrolysis, ethanol fermentation, and simultaneous saccharification and fermentation (SSF) process has been investigated.
Abstract: In this work, the effect of the addition of different concentrations of Tween-80 and three different zeolite-like products on enzymatic hydrolysis, ethanol fermentation, and simultaneous saccharification and fermentation (SSF) process has been investigated. The ability of these products to enhance the effectiveness of the SSF process to ethanol of steam-exploded poplar biomass using the thermotolerant strain Kluyveromyces marxianus EMS-26 has been tested.
TL;DR: In this paper, Lignocellulosic materials derived from forages, namely timothy grass, alfalfa, reed canary grass, and agricultural residues, such as corn stalks and barley straw, were pretreated using ammonia fiber explosion (AFEX) process.
Abstract: Lignocellulosic materials derived from forages, namely timothy grass, alfalfa, reed canary grass, and agricultural residues, such as corn stalks and barley straw, were pretreated using ammonia fiber explosion (AFEX) process. The pretreated materials were directly saccharified by cellulolytic enzymes. Sixty to 80% of theoretical yield of sugars were obtained from the pretreated biomasses. Subsequent ethanolic fermentation of the hydrolysates by Pachysolen tannophilus ATCC 32691 resulted in 40-60% of theoretical yield after 24 h, based on the sugars present in the hydrolysates. The uptake of sugars was not complete, indicating a possible inhibitory effect on P. tannophilus during the fermentation of these substrates.
TL;DR: A new approach is emphasized, namely adsorbents with immobilized histidine, which allows a good purification both in yield and purity of Abs, with the addi tional advantage of using gentle elution conditions.
Abstract: Antibodies (Abs) from the sera of patients with autoimmune diseases are reported to have different catalytic functions. Their recovery by effi cient purification methods is, therefore, a crucial step. This article reviews different available methods for their recovery and emphasizes a new approach, namely adsorbents with immobilized histidine, which allows a good purification both in yield and purity of Abs, with the addi tional advantage of using gentle elution conditions. This, in turn, will ensure the recovery of intact (nondenatured) catalytically functional Abs, directly from the sera.
TL;DR: The potatoes exploded at high pressure were hydrolyzed into a low molecular liquid starch, and then easily converted into ethanol by simultaneous saccharification and fermentation using mixed microorganisms: an amylolytic microorganism, Aspergillus awamori, and a fermentation microorganisms,Saccharomyces cerevisiae.
Abstract: Steam explosion pretreatment of potato for the efficient production of alcohol was experimentally studied. The amount of water-soluble starch increased with the increase of steam pressure, but the amounts of methanol-soluble material and Klason lignin remained insignificant, regardless of steam pressure. The potatoes exploded at high pressure were hydrolyzed into a low molecular liquid starch, and then easily converted into ethanol by simultaneous saccharification and fermentation using mixed microorganisms: an amylolytic microorganism, Aspergillus awamori, and a fermentation microorganism, Saccharomyces cerevisiae. The maximal ethanol concentration was 4.2 g/L in a batch culture at 15 g/L starch concentration, and 3.6 g/L in a continuous culture fed the same starch concentration. In the fed-batch culture, the maximal ethanol concentration increased more than twofold, compared to the batch culture.