Showing papers in "Journal of Industrial Microbiology & Biotechnology in 2000"

Ethanol production from seaweed extract

Abstract: Extracts from Laminaria hyperborea could possibly be fermented to ethanol commercially. In particular, seaweed harvested in the autumn contains high levels of easily extractable laminaran and mannitol. Four microorganisms were tested to carry out this fermentation, one bacterium and three yeasts. Only Pichia angophorae was able to utilise both laminaran and mannitol for ethanol production, and its substrate preferences were investigated in batch and continuous cultures. Laminaran and mannitol were consumed simultaneously, but with different relative rates. In batch fermentations, mannitol was the preferred substrate. Its share of the total laminaran and mannitol consumption rate increased with oxygen transfer rate (OTR) and pH. In continuous fermentations, laminaran was the preferred substrate at low OTR, whereas at higher OTR, laminaran and mannitol were consumed at similar rates. Optimisation of ethanol yield required a low OTR, and the best yield of 0.43 g ethanol (g substrate)−1 was achieved in batch culture at pH 4.5 and 5.8 mmol O2 l−1 h−1. However, industrial production of ethanol from seaweed would require an optimisation of the extraction process to yield a higher ethanol concentration. Journal of Industrial Microbiology & Biotechnology (2000) 25, 249–254.

Human pathogens associated with raw produce and unpasteurized juices, and difficulties in decontamination.

Abstract: The ability of public health agencies to identify, through enhanced epidemiologic and surveillance techniques, raw fruits, vegetables, and unpasteurized juices as probable sources of infectious microorganisms, has undoubtedly resulted in increased numbers of documented outbreaks. Changes in agronomic, harvesting, distribution, processing, and consumption patterns and practices have also likely contributed to this increase. The risk of illness associated with raw produce and unpasteurized produce products can be reduced by controlling or preventing contamination, or by removing or killing pathogenic microorganisms by washing or treating them with sanitizers. However, the hydrophobic cutin, diverse surface morphologies, and abrasions in the epidermis of fruits and vegetables limit the efficacy of these treatments.

Comparison of SHF and SSF processes for the bioconversion of steam-exploded wheat straw

Abstract: Two processes for ethanol production from wheat straw have been evaluated — separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). The study compares the ethanol yield for biomass subjected to varying steam explosion pretreatment conditions: temperature and time of pretreatment was 200°C or 217°C and at 3 or 10 min. A rinsing procedure with water and NaOH solutions was employed for removing lignin residues and the products of hemicellulose degradation from the biomass, resulting in a final structure that facilitated enzymatic hydrolysis. Biomass loading in the bioreactor ranged from 25 to 100 g l−1 (dry weight). The enzyme-to-biomass mass ratio was 0.06. Ethanol yields close to 81% of theoretical were achieved in the two-step process (SHF) at hydrolysis and fermentation temperatures of 45°C and 37°C, respectively. The broth required addition of nutrients. Sterilisation of the biomass hydrolysate in SHF and of reaction medium in SSF can be avoided as can the use of different buffers in the two stages. The optimum temperature for the single-step process (SSF) was found to be 37°C and ethanol yields close to 68% of theoretical were achieved. The SSF process required a much shorter overall process time (≈30 h) than the SHF process (96 h) and resulted in a large increase in ethanol productivity (0.837 g l−1 h−1 for SSF compared to 0.313 g l−1 h−1 for SHF). Journal of Industrial Microbiology & Biotechnology (2000) 25, 184–192.

Production of ethanol from mannitol by Zymobacter palmae.

Abstract: Extracts from brown seaweeds could possibly be fermented to ethanol, particularly seaweeds harvested in the autumn, which contain high levels of easily extractable laminaran and mannitol. Few microorganisms are able to utilise mannitol as a substrate for ethanol production and Zymobacter palmae was tested for this purpose. Bacterial growth as well as ethanol yield depended on the amount of oxygen present. Strictly anaerobic growth on mannitol was not observed. At excessive aeration, a change in the fermentation pattern was observed with high production of acetate and propionate. Under oxygen-limiting conditions, the bacteria grew and produced ethanol in a synthetic mannitol medium with a yield of 0.38 g ethanol (g mannitol)−1. Z. palmae was also successfully applied for fermentation of mannitol from Laminaria hyperborea extracts. Journal of Industrial Microbiology & Biotechnology (2000) 24, 51–57.

Production and characterization of thermostable xylanase and pectinase from Streptomyces sp. QG-11-3.

Abstract: Streptomyces sp. QG-11-3, which produces a cellulase-free thermostable xylanase (96 IU ml−1) and a pectinase (46 IU ml−1), was isolated on Horikoshi medium supplemented with 1% w/v wheat bran. Carbon sources that favored xylanase production were rice bran (82 IU ml−1) and birch-wood xylan (81 IU ml−1); pectinase production was also stimulated by pectin and cotton seed cake (34 IU ml−1 each). The partially purified xylanase and pectinase were optimally active at 60°C. Both enzymes were 100% stable at 50°C for more than 24 h. The half-lives of xylanase and pectinase at 70, 75 and 80°C were 90, 75 and 9 min, and 90, 53 and 7 min, respectively. The optimum pH values for xylanase and pectinase were 8.6 and 3.0, respectively, at 60°C. Xylanase and pectinase were stable over a broad pH range between 5.4 and 9.4 and 2.0 to 9.0, respectively, retaining more than 85% of their activity. Ca2+ stimulated the activity of both enzymes up to 7%, whereas Cd2+, Co2+, Cr3+, iodoacetic acid and iodoacetamide inhibited xylanase up to 35% and pectinase up to 63%; at 1 mM, Hg2+ inhibited both enzymes completely. Journal of Industrial Microbiology & Biotechnology (2000) 24, 396–402.

Advances in biotechnological production of butyric acid

Abstract: The review is focused on several aspects of butyric acid production: butyric acid-producing bacterial strains, the characteristics of the genus Clostridium (the bacterium most used for butyrate production), and alternative methods of obtaining butyric acid by alcohol biotransformation. Further, the main metabolic pathways of butyrate production, and possibilities for their control are outlined. Batch, fed-batch or continuous fermentation combined with cell recycle or immobilization are applicable for anaerobic fermentations using Clostridium as the production strain. The best process comprises a combination of high cell concentration and slowly growing biomass, in addition to high production selectivity and low inhibitory effects of the end-product. Inhibitory effects may be avoided by on-line removal of the end-product. Extraction alone or extraction combined with simultaneous stripping of the organic phase (liquid membrane) into the second aqueous phase (pertraction) seem to be the most suitable methods for on-line butyrate removal. The biocompatibility and the distribution coefficient of the organic phase under fermentation conditions should be considered before designing a fermentation apparatus. Journal of Industrial Microbiology & Biotechnology (2000) 24, 153–160.

Effect of pH on the biosorption of nickel and other heavy metals by Pseudomonas fluorescens 4F39

Abstract: Accumulation of heavy metals by Pseudomonas fluorescens 4F39 was rapid and pH-dependent. The affinity series for bacterial accumulation of metal cations decreased in the order Ni>>Hg>U>>As>Cu>Cd>Co>Cr>Pb. Metal cations were grouped into those whose accumulation increased as the pH increased, with a maximum accumulation at the pH before precipitation (Ni, Cu, Pb, Cd, Co), and those whose maximum accumulation was not associated with precipitation (Cr, As, U, Hg). High Ni2+ accumulation was studied. Electron microscopy indicated that at pH 9, Ni2+ accumulated on the cell surface as needle and hexagon-like precipitates, whose crystalline structure was confirmed by electron diffraction analysis and corresponded to two different orientations of the nickel hydroxide crystals. Crystals on cells showed marked anisotropy by X-ray powder diffraction, which differentiated them from crystals observed in nickel solution at pH 10 and 11 and from commercial nickel hydroxide. Nickel biosorption by Pseudomonas fluorescens 4F39 was a microprecipitation consequence of an ion exchange. Journal of Industrial Microbiology & Biotechnology (2000) 24, 146–151.

Production, purification and characterization of an extracellular inulinase from Kluyveromyces marxianus var. bulgaricus

Abstract: The yeast Kluyveromyces marxianus var. bulgaricus produced large amounts of extracellular inulinase activity when grown on inulin, sucrose, fructose and glucose as carbon source. This protein has been purified to homogeneity by using successive DEAE-Trisacryl Plus and Superose 6HR 10/30 columns. The purified enzyme showed a relative molecular weight of 57 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and 77 kDa by gel filtration in Superose 6 HR 10/30. Analysis by SDS-PAGE showed a unique polypeptide band with Coomassie Blue stain and nondenaturing PAGE of the purified enzyme obtained from media with different carbon sources showed the band, too, when stained for glucose oxidase activity. The optimal hydrolysis temperature for sucrose, raffinose and inulin was 55°C and the optimal pH for sucrose was 4.75. The apparent K m values for sucrose, raffinose and inulin are 4.58, 7.41 and 86.9 mg/ml, respectively. Thin layer chromatography showed that inulinase from K. marxianus var. bulgaricus was capable of hydrolyzing different substrates (sucrose, raffinose and inulin), releasing monosaccharides and oligosaccharides. The results obtained suggest the hypothesis that enzyme production was constitutive. Journal of Industrial Microbiology & Biotechnology (2000) 25, 63–69.

Citric and gluconic acid production from fig by Aspergillus niger using solid-state fermentation.

Abstract: The production of citric and gluconic acids from fig by Aspergillus niger ATCC 10577 in solid-state fermentation was investigated. The maximal citric and gluconic acids concentration (64 and 490 g/kg dry figs, respectively), citric acid yield (8%), and gluconic acid yield (63%) were obtained at a moisture level of 75%, initial pH 7.0, temperature 30°C, and fermentation time in 15 days. However, the highest biomass dry weight (40 g/kg wet substrate) and sugar utilization (90%) were obtained in cultures grown at 35°C. The addition of 6% (w/w) methanol into substrate increased the concentration of citric and gluconic acid from 64 and 490 to 96 and 685 g/kg dry fig, respectively. Journal of Industrial Microbiology & Biotechnology (2000) 25, 298–304.

Characterization of fluoranthene- and pyrene-degrading bacteria isolated from PAH-contaminated soils and sediments

Abstract: Sixteen environmental samples, from the United States, Germany and Norway, with histories of previous exposure to either creosote, diesel fuel or coal tar materials, were screened for bacteria which could degrade high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAHs). A modified version of the spray plate technique was used for the isolations. Using fluoranthene (FLA) and pyrene (PYR) as model HMW PAHs, we isolated 28 strains on FLA and 21 strains on PYR. FLA degraders were defined as able to grow on FLA but not PYR. PYR degraders grew on both PAHs. All PYR degraders were found to be Gram-positive and all FLA degraders were Gram-negative. GC-FAME analysis showed that many of the PYR degraders were Mycobacterium spp and many of the FLA degraders were Sphingomonas spp. Comparison of the metabolic characteristics of the strains using the spray plate technique and direct growth studies revealed that more than half of the FLA degraders (59%) were able to cometabolize PYR (ie, they produced clearing zones or colored metabolites on spray plates but did not grow on the PAH) and the ability of many of these strains to cometabolize fluorene, anthracene, benzo[b]fluorene, benzo[a]anthracene and benzo[a]pyrene was significantly affected by pre-exposure to phenanthrene. Studies on the metabolic products produced from PYR cometabolism by strain EPA 505 suggested the possibility of attack at two different sites on the PYR molecule. However, the inability to derive degradable carbon from initial opening of one of the PYR rings probably accounted for the lack of growth on this PAH by the FLA-degrading strains. The PYR degraders on the other hand, were less able to cometabolize HMW PAHs, even following pre-exposure to PHE. Characterization of the FLA degradation pathway for several of the Sphingomonas isolates indicated oxidation and ring opening through to acenaphthenone as the principle metabolite. Strain CO6, however, also oxidized FLA through fluorenone, suggesting a dual attack on the FLA molecule, similar to that observed by others in Mycobacterium spp. Journal of Industrial Microbiology & Biotechnology (2000) 24, 100–112.

Effects of mutations in acetate metabolism on high-cell-density growth of Escherichia coli

Abstract: To study the role played by acetate metabolism during high-cell-density growth of Escherichia coli cells, we constructed isogenic null mutants of strain W3100 deficient for several genes involved either in acetate metabolism or the transition to stationary phase. We grew these strains under identical fed-batch conditions to the highest cell densities achievable in 8 h using a predictive-plus-feedback-controlled computer algorithm that maintained glucose at a set-point of 0.5 g/l, as previously described. Wild-type strains, as well as mutants lacking the ss subunit of RNA polymerase (rpoS), grew reproducibly to high cell densities (44–50 g/l dry cell weights, DCWs). In contrast, a strain lacking acetate kinase (ackA) failed to reach densities greater than 8 g/l. Strains lacking other acetate metabolism genes (pta, acs, poxB, iclR, and fadR) achieved only medium cell densities (15–21 g/l DCWs). Complementation of either the acs or the ackA mutant restored wild-type high-cell-density growth. On a dry weight basis, poxB and fadR strains produced approximately threefold more acetate than did the wild-type strain. In contrast, the pta, acs, or rpoS strains produced significantly less acetate per cell dry weight than did the wild-type strain. Our results show that acetate metabolism plays a critical role during growth of E. coli cultures to high cell densities. They also demonstrate that cells do not require the ss regulon to grow to high cell densities, at least not under the conditions tested. Journal of Industrial Microbiology & Biotechnology (2000) 24, 421–430.

Growth inhibition of plant pathogenic fungi by hydroxy fatty acids

Abstract: Hydroxy fatty acids are plant self-defense substances (Masui et al, Phytochemistry1989). Three types of hydroxy fatty acids: 10-hydroxystearic acid (HSA), 7S,10S-dihydroxy-8(E)-octadecenoic acid (DOD), and 12,13,17-trihydroxy-9(Z)-octadecenoic acid (THOA) were tested against the following plant pathogenic fungi: Erysiphe graminis f sp tritici (common disease name, wheat powdery mildew); Puccinia recondita (wheat leaf rust); Pseudocercosporella herpotrichoides (wheat foot rot); Septoria nodorum (wheat glume blotch); Pyricularia grisea (rice blast); Rhizoctonia solani (rice sheath blight); Phytophthora infestans (potato late blight); and Botrytis cinerea (cucumber botrytis). At a concentration of 200 ppm, both HSA and DOD showed no fungal disease control activity. However, THOA at the same concentration showed weak activity and provided disease control (percent) of the following plant pathogenic fungi: Erysiphe graminis 77%; Puccinia recondita 86%; Phytophthora infestans 56%; and Botrytis cinerea 63%. The position of the hydroxy groups on the fatty acids seems to play an important role in activity against specific fungi. Journal of Industrial Microbiology & Biotechnology (2000) 24, 275–276.

Industrial media and fermentation processes for improved growth and protease production by Tetrahymena thermophila BIII

Abstract: was cultivated on industrial by-product media. The composition of the best medium (with milk proteins) was optimised by a central composite design for growth and protease secretion. The optimal combination [1.07% (w/v) of yeast extract and 0.99% (w/v) of skimmed milk] improved biomass production by 46%. In a fermentation strategy, the pH must be regulated to produce no cell damage, lengthening the stationary phase and resulting in a more abundant protease production. To increase cell concentration and protease secretion, a continuous culture with cell recycling by microfiltration was successfully tested on ciliated protozoa. Journal of Industrial Microbiology & Biotechnology (2000) 24, 285–290.

Use of bioluminescent Salmonella for assessing the efficiency of constructed phage-based biosorbent.

Abstract: A bacteriophage-based biosorbent for Salmonella enteritidis was constructed, and bacterial bioluminescence was used for assessment of the efficiency of cell capture. A strain of S. enteritidis with bioluminescent phenotype was constructed by transformation with plasmid pT7 carrying the entire lux operon from Photorhabdus luminescens. The relation between relative light output (RLU) and colony-forming units (CFU/ml) of the bioluminescent strain was established. The bacteriophage specific to S. enteritidis was biotinylated, and the biotinylation procedure was optimized based on the maximum retention of phage infectivity. The biotinylated phages were then coated onto streptavidin-labeled magnetic beads, and were used to capture the bioluminescent S. enteritidis cells. Our preliminary results showed that the number of cells captured by constructed biosorbent was five times higher than that of the control, magnetic beads coated with nonbiotinylated phage, indicating the capture is specific.

Heterotrophic production of eicosapentaenoid acid by the diatom Nitzschia laevis: effects of silicate and glucose

Abstract: The effects of silicate and glucose on growth and eicosapentaenoic acid (EPA) production by the diatom Nitzschia laevis were studied. By alternately altering the concentrations of silicate (2.7–64 mg l−1) and glucose (1–40 g l−1) in the medium, the highest cell dry weight (ca. 5.5 g l−1) was obtained at 20 g l−1 glucose and 32 mg l−1 silicate, while the highest specific growth rate (ca. 0.65 day−1) was obtained at a relatively low glucose concentration (5 g l−1) and high silicate concentrations (32–64 mg l−1). At glucose levels of 5 and 20 g l−1, EPA content was higher with lower silicate concentrations (2.7 and 16 mg l−1 silicate, respectively), while at a silicate level of 16 mg l−1, higher glucose concentrations (20–40 g l−1) facilitated EPA formation. The highest EPA yield (131 mg l−1) was obtained at 20 g l−1 glucose and 32 mg l−1 silicate, while the highest EPA productivity (15.1 mg l−1 day−1) was obtained at 20 g l−1 glucose and 64 mg l−1 silicate. Journal of Industrial Microbiology & Biotechnology (2000) 25, 218–224.

Biosynthesis of tannin acyl hydrolase from tannin-rich forest residue under different fermentation conditions

Abstract: Caesalpinia digyna, a tannin-rich forest residue, was used as substrate for production of tannase and gallic acid. Media engineering was carried out under solid-state fermentation, submerged fermentation and modified solid state fermentation conditions for optimum synthesis of tannase and gallic acid (based on 58% tannin content in the raw material). Tannase vis-a-vis gallic acid recovery under modified solid-state fermentation condition was maximum. Conversions of tannin to gallic acid under solid-state fermentation, submerged fermentation and modified solid-state fermentation conditions were 30.5%, 27.5% and 90.9%, respectively. Journal of Industrial Microbiology & Biotechnology (2000) 25, 29–38.

An optimization study of carotenoid production by Rhodotorula glutinis DBVPG 3853 from substrates containing concentrated rectified grape must as the sole carbohydrate source

Abstract: A multivariate statistical approach was employed for the optimization of conditions for carotenoid production by Rhodotorula glutinis DBVPG 3853 from a substrate containing concentrated rectified grape must as the sole carbohydrate source. Several experimental parameters (carbohydrate, yeast autolysate and salt concentrations, and pH) were tested at two levels by following a fractional factorial design. Carotenogenesis was most sensitive to both initial pH and yeast autolysate concentration. A Central Composite Design experiment was then performed by obtaining both second-order polynomial models and isoresponse diagrams where initial pH and yeast autolysate concentration were considered as variables. In this way it was possible to determine the conditions (pH = 5.78, yeast autolysate = 4.67 g L−1) which maximize both the concentration of total carotenoids and that of β-carotene (6.9 mg L−1 and 1100 μg L−1 of culture fluid, respectively, after 120 h of fermentation). Journal of Industrial Microbiology & Biotechnology (2000) 24, 41–45.

Chromate reduction by Rhodobacter sphaeroides

Abstract: grew in the presence of up to 43 μM chromate and reduced hexavalent chromium to the trivalent form under both aerobic and anaerobic conditions. Reduced chromium remained in the external medium. Reductase activity was present in cells of R. sphaeroides independent of whether chromate was present or not in the growth medium. The reducing activity was found in the cytoplasmic cell fraction and was dependent on NADH. The chromate-reducing enzyme was purified by anion exchange, hydroxyapatite and hydrophobic interaction chromatography, and gel filtration. The molecular weight of the enzyme was 42 kDa as determined by gel filtration. The optimum of the reaction is at pH 7.0 and 30°C. The enzyme activity showed a hyperbolic dependence on the concentrations of both substrates, NADH and chromate, with a maximum velocity at 0.15 mM NADH. A K m of 15±1.3 μM CrO4 2− and a V max of 420±50 μmol min−1 mg protein−1 was determined for the enzyme isolated from anaerobically grown cells and 29±6.4 μM CrO4 2− and 100±9.6 μmol CrO4 2− min−1 mg protein−1 for the one from aerobically grown ones. Journal of Industrial Microbiology & Biotechnology (2000) 25, 198–203.

Comparison of exopolysaccharide production by strains of Lactobacillus rhamnosus and Lactobacillus paracasei grown in chemically defined medium and milk

Abstract: Exopolysaccharide (EPS) production was compared among three strains of lactobacilli. Lactobacillus rhamnosus strain 9595M can be classified among the highest EPS-producing strains of lactic acid bacteria reported to date with a maximum EPS production of 1275 mg L−1. Under controlled pH, no significant differences in the quantity of EPS produced could be detected between carbon source (glucose or lactose) or fermentation temperature (32 or 37°C). In milk, strains ATCC 9595M and R produced more than 280 mg L−1 EPS whereas strain Type V produced less than 80 mg L−1 EPS. Journal of Industrial Microbiology & Biotechnology (2000) 24, 251–255.

Production of high activity thermostable phytase from thermotolerant Aspergillus niger in solid state fermentation

Abstract: The thermotolerant fungus, Aspergillus niger NCIM 563, was used for production of extracellular phytase on agricultural residues: wheat bran, mustard cake, cowpea meal, groundnut cake, coconut cake, cotton cake and black bean flour in solid state fermentation (SSF). Maximum enzyme activity (108 U g−1 dry mouldy bran, DMB) was obtained with cowpea meal. During the fermentation phytic acid was hydrolysed completely with a corresponding increase in biomass and phytase activity within 7 days. Phosphate in the form of KH2PO4 (10 mg per 100 g of agriculture residue) increased phytase activity. Among various surfactants added to SSF, Trition X-100 (0.5%) exhibited a 30% increase in phytase activity. The optimum pH and temperature of the crude enzyme were 5.0 and 50°C respectively. Phytase activity (86%) was retained in buffer of pH 3.5 for 24 h. The enzyme retained 75% of its activity on incubation at 55°C for 1 h. In the presence of 1 mM K+ and Zn2+, 95% and 55% of the activity were retained. Scanning electron microscopy showed a high density growth of fungal mycelia on wheat bran particles during SSF. Journal of Industrial Microbiology & Biotechnology (2000) 24, 237–243.

Monitoring bioremediation in creosote-contaminated soils using chemical analysis and toxicity tests.

Abstract: Three soils with a history of creosote contamination (designated NB, TI and AC) were treated in bench-scale microcosms using conditions (nutrient amendment, moisture content and temperature) which had promoted mineralization of 14C-pyrene in a preliminary study. Bioremediation was monitored using the solid-phase Microtox test, seed germination and earthworm survival assays, SOS-chromotest, Toxi-chromotest and a red blood cell (RBC) haemolysis assay. Contaminant concentrations in the AC soil did not change after 150 days. Polycyclic aromatic hydrocarbon (PAH) concentrations decreased in the NB soil, and toxicity decreased overall according to the earthworm, seed germination and Microtox tests. Although total petroleum hydrocarbons (TPHs) in the TI soil were reduced following treatment, results of the earthworm, seed germination, RBC and Microtox tests suggested an initial increase in toxicity indicating that toxic intermediary metabolites may have formed during biodegradation. Toxicity testing results did not always correlate with contaminant concentrations, nor were the trends indicated by each test consistent for any one soil. Each test demonstrated a different capacity to detect reductions in soil contamination. Journal of Industrial Microbiology & Biotechnology (2000) 24, 132–139.

Optimization of erythritol production by Candida magnoliae in fed-batch culture.

Abstract: A two-stage fed-batch process was designed to enhance erythritol productivity by the mutant strain of Candida magnoliae. The first stage (or growth stage) was performed in the fed-batch mode where the growth medium was fed when the pH of the culture broth dropped below 4.5. The second stage (or production stage) was started with addition of glucose powder into the culture broth when the cell mass reached about 75 g dry cell weight l−1. When the initial glucose concentration was adjusted to 400 g l−1 in the production stage, 2.8 g l−1 h−1 of overall erythritol productivity and 41% of erythritol conversion yield were achieved, which represented a fivefold increase in erythritol productivity compared with the simple batch fermentation process. A high glucose concentration in the production phase resulted in formation of organic acids including citrate and butyrate. An increase in dissolved oxygen level caused formation of gluconic acid instead of citric acid. Journal of Industrial Microbiology & Biotechnology (2000) 25, 100–103.

Production of carotenoids by Brevibacterium linens: variation among strains, kinetic aspects and HPLC profiles

Abstract: This work describes carotenoid pigment production by the red bacterium Brevibacterium linens covering strain diversity, kinetic and analytical aspects. Pigment production of 23 B. linens strains ranged from 0.05 to 0.60 mg pigments L−1 culture, with specific productivity from 0.2 to 0.6 mg pigments per g dry biomass. The pigment production time curve showed a sigmoid shape, that matched cell growth. HPLC analysis revealed three groups of peaks, possibly non-hydroxylated, mono- and di-hydroxylated carotenoids. Polar molecules were mainly represented. Journal of Industrial Microbiology & Biotechnology (2000) 24, 64–70.

Large-scale production of GDP-fucose and Lewis X by bacterial coupling

Abstract: A large-scale production system of GDP-fucose (GDP-Fuc) and fucosylated oligosaccharides was established by the combination of recombinant Escherichia coli cells overexpressing GDP-Fuc biosynthetic genes and Corynebacterium ammoniagenes cells. E. coli cells overexpressed the genes for glucokinase, phosphomannomutase, mannose-1-phosphate guanylyltransferase, GDP-mannose (GDP-Man) dehydratase, and GDP-4-keto-6-deoxy-mannose (GKDM) epimerase/reductase as well as phosphoglucomutase and phosphofructokinase. C. ammoniagenes contributed to the formation of GTP from GMP. GDP-Fuc accumulated to 29 mM (18.4 g l−1) after a 22-h reaction starting with GMP and mannose through introducing the two-step reaction to overcome the inhibition of GDP-Fuc on GDP-Man dehydratase activity. When E. coli cells overexpressing the α1,3-fucosyltransferase gene of Helicobacter pylori were put into the GDP-Fuc production system, Lewis X [Galβ1–4(Fucα1–3)GlcNAc] was produced at an amount of 40 mM (21 g l−1) for 30 h from GMP, mannose, and N-acetyl lactosamine. The production system through bacterial coupling can be applied to the industrial manufacture of fucosylated oligosaccharides. Journal of Industrial Microbiology & Biotechnology (2000) 25, 213–217.

ORIGINAL PAPERS Biosorption of U, La, Pr, Nd, Eu and Dy by Pseudomonas aeruginosa

Abstract: Kinetic studies with Pseudomonas aeruginosa using actinides and lanthanides indicated a two-phase metal uptake. Equilibrium uptake data of all the metals studied could be fitted to Langmuir as well as Freundlich models. The Scatchard plots showed that there were mainly two types of receptor sites on the cell walls of P. aeruginosa having different affinities for the metal ions. EDAX studies revealed replacement of calcium and magnesium ions from biomass by sorbed metal. Around 85% of the adsorbed metal could be released using citrate buffer (pH 4.0, 0.2 M). Metal desorption was as high as 95% with HCl. Continuous flow studies using P. aeruginosa immobilized on activated alumina gave 80% enhancement of lanthanum removal efficiency compared to the control column. Regeneration of the column resulted in 80% of its initial capacity in succeeding cycles. Journal of Industrial Microbiology & Biotechnology (2000) 25, 1–7.

LC-NMR: a new tool to expedite the dereplication and identification of natural products.

Abstract: The rapid identification of known or undesirable compounds from natural products extracts — “dereplication” — is an important step in an efficiently run natural products discovery program. Dereplication strategies use analytical techniques and database searching to determine the identity of an active compound at the earliest possible stage in the discovery process. In the past few years, advances in technology have allowed the development of tandem analytical techniques such as liquid chromatography mass spectrometry (LC-MS), LC-MS-MS, liquid chromatography nuclear magnetic resonance (LC-NMR), and LC-NMR-MS. LC-NMR, despite its lower sensitivity as compared to LC-MS, provides a powerful tool for rapid identification of known compounds and identification of structure classes of novel compounds. LC-NMR is especially useful in instances where the data from LC-MS are incomplete or do not allow confident identification of the active component of a sample. LC-NMR has been used to identify the marine alkaloid aaptamine as the active component in an extract of the sponge Aaptos sp. This extract had been identified as an enzyme inhibitor by a high throughput screening (HTS) effort. Isolated aaptamine exhibited an IC50=120 μM against this enzyme. Strategies for the identification of aaptamine and for the use of LC-NMR in a natural products HTS program are discussed. Journal of Industrial Microbiology & Biotechnology (2000) 25, 342–345.

Bacterial exopolysaccharides produced by newly discovered bacteria belonging to the genus Halomonas , isolated from hypersaline habitats in Morocco

Abstract: We have studied the exopolysaccharides (EPS) from a new group of moderately halophilic bacteria belonging to the genus Halomonas. The quantity of EPS produced, its chemical composition and physical properties depend greatly upon the bacterial strain. The majority of the polymers produced viscous solutions and/or emulsified different hydrocarbon compounds. The most interesting strain, S-30, produced EPS at 2.8 g/l with a maximum viscosity of 23.5 Pa·5 and exhibited pseudoplastic behavior. This EPS emulsified five hydrocarbons more efficiently than did four control surfactants tested. Its monosaccharide composition was glucose:galactose:manose:glucuronic acid in equimolar ratio. Some two-thirds of the strains tested emulsified crude oil better than control surfactants did. There are many potential industrial applications for polysaccharides with these qualities. Journal of Industrial Microbiology & Biotechnology (2000)24, 374–378.

Purification and characterization of an alkaline protease from Pseudomonas aeruginosa MN1

Abstract: An alkaline protease produced by Pseudomonas aeruginosa MN1, isolated from an alkaline tannery waste water, was purified and characterized. The enzyme was purified 25-fold by gel filtration and ion exchange chromatography to a specific activity of 82350 U mg−1. The molecular weight of the enzyme was estimated to be 32000 daltons. The optimum pH and temperature for the proteolytic activity were pH 8.00 and 60°C, respectively. Enzyme activity was inhibited by EDTA suggesting that the preparation contains a metalloprotease. Enzyme activity was strongly inhibited by Zn2+, Cu2+ and Hg2+(5 mM), while Ca2+ and Mn2+ resulted in partial inhibition. The enzyme is different from other Pseudomonas aeruginosa alkaline proteases in its stability at high temperature; it retained more than 90% and 66% of the initial activity after 15 and 120 min incubation at 60°C. Journal of Industrial Microbiology & Biotechnology (2000) 24, 291–295.

High alcohol production by repeated batch fermentation using an immobilized osmotolerant Saccharomyces cerevisiae

Abstract: A repeated batch fermentation system was used to produce ethanol using an osmotolerant Saccharomyces cerevisiae (VS3) immobilized in calcium alginate beads. For comparison free cells were also used to produce ethanol by repeated batch fermentation. Fermentation was carried for six cycles with 125, 250 or 500 beads using 150, 200 or 250 g glucose L−1 at 30°C. The maximum amount of ethanol produced by immobilized VS3 using 150 g L−1 glucose was only 44 g L−1 after 48 h, while the amount of ethanol produced by free cells in the first cycle was 72 g L−1. However in subsequent fed batch cultures more ethanol was produced by immobilized cells compared to free cells. The amount of ethanol produced by free cells decreased from 72 g L−1 to 25 g L−1 after the fourth cycle, while that of immobilized cells increased from 44 to 72 g L−1. The maximum amount of ethanol produced by immobilized VS3 cells using 150, 200 and 250 g glucose L−1 was 72.5, 93 and 87 g ethanol L−1 at 30°C. Journal of Industrial Microbiology & Biotechnology (2000) 24, 222–226.

Effects of elevated temperature on bacterial community structure and function in bioreactors treating a synthetic wastewater

Abstract: The impact of elevated temperature on bacterial community structure and function during aerobic biological wastewater treatment was investigated. Continuous cultures, fed a complex growth medium containing gelatin and α-lactose as the principal carbon and energy sources, supported mixed bacterial consortia at temperatures ranging from 25–65°C. These temperature- and substrate-acclimated organisms were then used as inocula for batch growth experiments in which the kinetics of microbial growth and substrate utilization, efficiency of substrate removal, and mechanism of substrate removal were compared as functions of temperature. Bacterial community analysis by denaturing gradient gel electrophoresis (DGGE) revealed that distinct bacterial consortia were supported at each temperature. The efficiency of substrate removal declined at elevated temperatures. Maximum specific growth rates and the growth yield increased with temperature from 25–45°C, but then decreased with further elevations in temperature. Thus, maximum specific substrate utilization rates did not vary significantly over the 40°C temperature range (0.64 ± 0.04 mg COD mg−1 dry cell mass h−1). A comparison of the degradation of the protein and carbohydrate portions of the feed medium revealed a lag in α-lactose uptake at 55°C, whereas both components were utilized simultaneously at 25°C. Journal of Industrial Microbiology & Biotechnology (2000) 24, 140–145.