Production of fatty acids and lipid by a Candida sp. growing on a fraction of n-alkanes predominating in tridecane

A Candida sp. was grown on a fraction of n-alkanes (dodecane 22%, tridecane 48%, tetradecane 28%) as sole carbon source. The growth rate was increased most markedly by using high concentrations of n-alkanes (16.7% v/v). When grown in a 5 liter fermentor, the yeast reached its highest yield (60 g. of cell dry wt/l) with a concomitant high yield of fatty acids (21 g of fatty acids/l), by using a nitrogen-deficient medium. To achieve good growth, it was essential to use an inoculum (1 part into 10) of rapidly growing cells and beneficial to increase the agitation rate gradually once growth had begun. After 108 hr maximum conversions of substrate to product were: 71.5% (w/w) for alkanes into cells and 24.8% (w/w) for alkanes into fatty acids. Of the, total fatty acids at the end of the fat-accumulating phase of growth 54% were shorter in chain length than palmitic acid (C₁₆H₃₂O₂). When grown on glucose, as sole carbon source, less than 2% of the total fatty acids were shorter than palmitic acid. When n-alkanes were added to cells growing on glucose, short-chain fatty acids (C₁₀ to C₁₄) were synthesized immediately, indicating a derepressed enzyme system for hydrocarbon assimilation and the absence of diauxie. The production of these acids was at the apparent sacrifice of linoleic acid synthesis. In spite of the high conversion ratios, it is concluded that it would be uneconomical to produce fatty acids, even expensive ones such as lauric acid, by microbial transformation of n-alkanes.     

Food Quality Constraints in Daphnia: Interspecific Differences in the Response to the Absence of a Long Chain Polyunsaturated Fatty Acid in the Food Source

The effect of the long chain polyunsaturated fatty acid (PUFA) eicosapentaenoic acid (EPA, 20:53) on food quality for Daphnia galeata, Daphnia hyalina and a D. galeata×hyalina hybrid was examined. Somatic growth rates of all three species were determined when growing on EPA-free Scenedesmus obliquus and on S. obliquus which had been supplemented with free EPA prior to the growth experiments. Growth rates on S. obliquus were substantially higher in D. galeata(0.45day^–1) than in D. hyalina(0.27day^–1) and D. galeata×hyalina(0.31day^–1). Supplementary EPA increased growth of D. galeata and D. hyalina, but not of the hybrid. Hence within the D. galeata/hyalina complex species differ in their ability to cope with an EPA-free diet. Analysis of fatty acids revealed that tissue concentrations of 18:33, 18:43, 20:33 and 20:43 were higher in D. galeata than in D. hyalina which indicated higher rates of assimilation and biosynthesis of PUFAs in D. galeata. This was contrasted by lower tissue concentrations of 20:53 D. galeata than in D. hyalina which suggests that 20:53 is metabolised with growth. In the D. galeata×hyalina hybrid high PUFA assimilation and biosynthesis were associated with low growth rates which explains the finding that tissue concentrations of 20:53 were highest and that growth was not constrained by the availability of 20:53.     

Solubilization of tricalcium phosphate by P(3HB) accumulating Azotobacter chroococcum MAL-201

Cells of Azotobacter chroococcum MAL-201 (MTCC 3853) are capable of accumulating the intracellular poly(3-hydroxybutyric acid) [P(3HB)], accounting for 65–71 % of its cell dry weight and also capable of synthesizing the enzyme alkaline phosphatase (APase), when grown in glucose and tricalcium phosphate containing nitrogen-free modified Stockdale medium. The concentration of insoluble phosphate in broth medium was optimized as 0.25 % (w/v) for growth and biosynthesis of APase. However, the suboptimal concentration of phosphate (0.1 %, w/v) appeared as the best suited for accumulation of P(3HB) by the strain. The significant differences were observed in biosynthesis of polymer and APase enzyme under variable phosphate concentrations. Glucose, 3.0 % (w/v) was recorded as the optimum concentration for all of the three parameters. The continuation of APase biosynthesis was observed during the period of significant decline in the cellular content of the polymer in the late phase of growth. In order to study the role of P(3HB), the rate of autodigestion of biopolymer and phosphate solubilization rate (k, mineralization constant) were determined in carbon-free medium under batch cultivation process and the parameters were found to be positively correlated. The maximum phosphate solubilization rate (k = 0.0154) by the strain MAL-201 timed at the 10th hour of incubation when the rate of polymer degradation concomitantly attained its peak corresponding to 87 mg/l/h and then declined gradually. Only a negligible amount of residual polymer remained undigested. These data strongly support the functional role of P(3HB) in response to multinutritional stress condition.     

Microbial hydrogen production with Bacillus coagulans IIT-BT S1 isolated from anaerobic sewage sludge

Bacillus coagulans strain IIT-BT S1 isolated from anaerobically digested activated sewage sludge was investigated for its ability to produce H(2) from glucose-based medium under the influence of different environmental parameters. At mid-exponential phase of cell growth, H(2) production initiated and reached maximum production rate in the stationary phase. The maximal H(2) yield (2.28 mol H(2)/molglucose) was recorded at an initial glucose concentration of 2% (w/v), pH 6.5, temperature 37 degrees C, inoculum volume of 10% (v/v) and inoculum age of 14 h. Cell growth rate and rate of hydrogen production decreased when glucose concentration was elevated above 2% w/v, indicating substrate inhibition. The ability of the organism to utilize various carbon sources for H(2) fermentation was also determined.     

Influence of carbon source on growth,biochemical composition and pigmentation of Ankistrodesmus convolutus

The unicellular chlorophyte Ankistrodesmus convolutus Corda was grown in the light using inorganic medium (Bold's Basal Medium, BBM) and BBM enriched with 0.1% w/v of glucose, sodium acetate, sodium citrate or sodium bicarbonate. Glucose supported the highest specific growth rate (μ = 0.93 d^-1) and gave the highest biomass (453 mg dry weight L^-1) at the time of harvest. Of four glucose concentrations (0.05, 0.1, 0.25, 0.5% w/v), best growth was attained at 0.1% w/v. At 0.5% w/v glucose, the cells had high carbohydrates but low lipids and proteins. The relative amounts of 16:0, 18:0, 18:1 and 18:2 increased at the expense of 18:3(n-3) in the carbon-supplemented cultures and at glucose concentrations higher than 0.1% w/v. Cultures grown on glucose had less chlorophyll and carotenoid contents than cultures grown on other carbon sources. Chlorophyll and carotenoid contents decreased with increasing glucose concentrations in the medium.     

Effect of yeast extract supplementation in leach solution on bioleaching rate of pyrite by acidophilic thermophile acidianus brierleyi

The bioleaching rate of pyrite (FeS2) by the acidophilic thermophile Acidianus brierleyi was studied at 65 degrees C and pH 1.5 with leach solutions supplemented with yeast extract. In the absence of yeast extract supplementation, A. brierleyi could grow autotrophically on pyrite, and the leaching percentage of pyrite particles (25-44 μm) reached 25% for 7 d. The bacterial growth and consequent pyrite oxidation were enhanced by the addition of yeast extract between 0.005 and 0.25% w/v: the pyrite particles were completely solubilized within 6 d. The bioleaching rate was enhanced by a factor of 1.5 when the yeast extract concentration was changed from 0.005 to 0.05% w/v. However, there was only a slight effect on the leaching rate at the yeast extract concentrations of 0.05 to 0. 25% w/v, suggesting that the organic supplement level was in large excess in the pyrite bioleaching. Copyright 1998 John Wiley & Sons, Inc.     

Saccharification and protein enrichment of sugar beet pulp byPleurotus florida

Summary Pleurotus florida was grown in submerged culture with different concentrations of sugar beet pulp with a view to its nutritional upgrading. Micelial growth, protein enrichment and dry weight loss of the solid residues of cultures, as well as the evolution of reducing sugars in the liquid medium, were followed for 14 days. A product with 45% (w/w) protein and a saccharification extent as high as 35% (w/w) were obtained after 7 days with 1% (w/v) sugar beet pulp.     

Evaluation of culture medium for nisin production in a repeated-batch biofilm reactor

In this study, a biofilm reactor with plastic composite support (PCS), made by high-temperature extrusion of agricultural products and polypropylene, was evaluated for nisin production using L. lactis strain NIZO 22186. The high-biomass density of the biofilm reactor was found to contribute to a significantly shorter lag time of nisin production relative to a suspended-cell reactor. In comparison to glucose (579 IU/mL), sucrose significantly increased the nisin production rate by 1.4-fold (1100 IU/mL). However, results revealed that high levels of sucrose (8% w/v) had a suppressing effect on nisin production and a stimulating effect on lactic acid production. A high concentration of MgSO4.7H2O at 0.04% (w/v) was found to reduce the nisin production, while concentrations of KH2PO4 of up to 3% (w/v) did not have any significant effect on growth or nisin production. The best of the tested complex media for nisin production using the PCS biofilm reactor consisted of 4% (w/v) sucrose, 0.02% (w/v) MgSO4.7H2O, and 0.1% (w/v) KH2PO4. Nisin production rate in the biofilm reactor was significantly increased by 3.8-fold (2208 IU/mL) when using the best complex medium tested.     

The cryopreservation of Chlorella 1. Interactions of rate of cooling,protective additive and warming rate

The cryoprotective additives glycerol and dimethylsulphoxide were found to be toxic to Chlorella cells at concentrations greater then 2.5% w/v. Polyvinylpyrrolidone, was not damaging up to a concentration of 15% w/v. Chlorella 211/7a had a recovery rate greater than 95% at all rates of cooling studied. With Chlorella 211/8h the survival was lower than 0.1% at all rates examined. The addition of dimethylsulphoxide (5% w/v) to Chlorella 211/8h increased the recovery, particularly at the faster rates of cooling; with polyvinylpyrrolidone (10% w/v) there was an optimum range of cooling rate.Cells of Chlorella 211/7a from the exponential phase of growth were found to be damaged both by a temperature reduction from 25°C to 0°C (thermal shock) and by freezing and thawing. In contrast cells from the stationary phase of growth were resistant to these stresses.Abbreviations DMSO dimethylsulphoxide - HEPES N-2-hydroxyethylpiperazine-N-2-ethansulphonic acid - PVP polyvinylpyrrolidone     

Regulation of Gibberellin Biosynthesis in Gibberella fujikuroi

Gibberellin production by Gibberella fujikuroi started only after the nitrogen source was depleted and ceased upon its renewal. Nitrogen repression of gibberellin biosynthesis is not an indirect effect of the growth arrest that follows the depletion of an essential nutrient because gibberellins were not produced upon depletion of phosphate. Mycelia produced gibberellins when suspended in a glucose solution. Production ceased some time after depletion of glucose and resumed upon its readdition. Under certain conditions, the gibberellin production rate was inversely proportional to the glucose concentrations. The specific regulation of gibberellin biosynthesis by the nitrogen source imposes a revision of the concept that gibberellins are secondary metabolites whose production is triggered by imbalance or cessation of growth.     

Ethanol production by Zymomonas mobilis in fed-batch fermentations

The production of ethanol by Zymomonas mobilis NRRL B-4286 was studied in fed-batch cultures. Initial percent (w/v) glucose, rate of feed, and quantity of 50%; (w/v) glucose feed were varied. Glucose inhibition of growth rate occurred at concentrations greater than 8% (w/) Feed was begun after 4 h incubation. Feed volume was ca. 36%; of starting batch volume to get ca. 10%; (w/v) ethanol at harvest. The range of feed rates studied varied from 16%; batch volume/h (glucose concentration increased to an inhibitory level) to 4%; batch volume/h (glucose concentration dropped rapidly to zero and was limiting). Increasing feed volume to 46%; of starting volume at the best feed rate (ca. 10%; feed volume/h) increased final ethanol concentration to 11.3%; (w/v). However, the resultant increase in fermentation time from ca. 21 to 29 h decreased ethanol volumetric productivity from 5.2 to 4.6 g/L h.     

Response surface methodology for optimizing the fermentation medium of Clostridium butyricum

AIMS: Strains of Clostridium butyricum have been increasingly used as probiotics for both animals and humans. The aim of this study was to develop a growth medium for cultivating C. butyricum ZJUCB using a statistical methodology. METHODS AND RESULTS: Response surface methodology (RSM) was used to evaluate the effects of variables, namely the concentrations of the glucose, pectin, soyabean cake extract, casein, corn steep flour, ammonium sulphate, sodium bicarbonate and the medium initial pH. A fractional factorial design was applied to study the main factors that affected the growth of a probiotic strain of C. butyricum currently preserved in our lab and the central composite experimental design was adopted to derive a statistical model for optimizing the composition of the fermentation medium. The experimental results showed that the optimum fermentation medium for the growth of C. butyricum was composed of 2% glucose (w/v), 0.5% pectin (w/v), 0.2% casein (w/v), 3.98% soyabean cake extract, 0.1% (NH4)2SO4 (w/v), 0.124% NaHCO3 (w/v), 0.37% corn steep flour (w/v), 0.02% MnSO4 H2O (w/v), 0.02% MgSO4 7H2O (w/v) and 0.002% CaCl2 (w/v) at pH 7.5. CONCLUSIONS: After incubating 24 h in the optimum fermentation medium, the populations of the viable organisms were estimated to be 10(9) CFU ml(-1). In the present study, we report the optimization of a growth medium that produced increased yields using statistical approach. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of bacteria as a probiotic is showing increasing potential. The development of a growth medium that has a high yield is an obvious need, and the approach to optimizing a growth medium is innovative.     

Growth and butyric acid production by Clostridium populeti

The growth of Clostridium populeti in 2% (w/v) glucose medium containing 0.2% (w/v) yeast extract was optimal with 10 mM NH₄Cl as the nitrogen source. Although the maximum specific growth rate (=0.32 h^-1) with 5 mM NH₄Cl was similar, the biomass yield was about 30% lower than that at the optimum. Either sodium sulphide or cysteine-HCl at an optimum concentration of 0.33 mM and 5.0 mM respectively, could serve as the sole sulphur source for growth. The growth rate was unaffected by initial glucose concentrations of up to 10% (w/v), but in the presence of 15% glucose it declined by about 35%. The molar yield of butyric acid (mol/mol glucose) declined from 0.70 in 1% (w/v) initial glucose medium to 0.39 in 10% glucose medium. In 5.7% initial glucose medium, butyric acid levels of 6.3 g/l were obtained (0.56 mol butyrate/mol glucose) after 72 h of incubation in 2.5 l batch cultures. A decrease of about 50% in the maximum specific growth rate of C. populeti was observed in the presence of an initial concentration of either 1.2 g/l of butyric acid or 18.9 g/l of acetic acid.This paper is issued as NRCC No. 29032     

Enantiocomplementary reduction of 3-phenylthiopropan-2-one by Bacillus sp.: effect of medium components

The enantioselectivity of the enzymes responsible for reduction of prochiral compound 3-phenylthiopropan-2-one was dependent on the concentration of yeast extract and glucose in the growth medium. Low concentrations of yeast extract (0.1-0.9% w/v) favored the formation of S-enantiomer (62% ee at 0.1% w/v yeast extract) of 3-phenylthiopropan-2-ol. However, R-enantiomer of the reduced product was formed when MSM was supplemented with yeast extract at a concentration of 1% (w/v) or more with a maximum ee of 85% at 2.0% (w/v) yeast extract supplement in the growth medium.     

Arabitol accumulation in Geotrichum candidum

Culture conditions which lead to the intracellular accumulation of arabitol and mannitol in Geotrichum candidum were investigated. The accumulation of arabitol was dependent on the concentrations of metabolizable hexoses, the non-metabolizable disaccharide sucrose, NaCl and KCl in the growth medium. In media containing 2% (w/v) glucose, fructose or l-sorbose cultures contained only mannitol after 48 h or 72 h growth. In media containing 10% (w/v) to 30% (w/v) glucose, or 25% (w/v) fructose or l-sorbose there was an increase in the total concentration of intracellular polyol due to the accumulation of arabitol. This pentitol was also found to accumulate intracellularly when the organism was grown in medium containing 34% (w/v) sucrose, 0.7 M NaCl or 0.7 M KCl in addition to 2% (w/v) glucose. Under the conditions tested no change in the accumulation of mannitol or ethanol-soluble carbohydrate, believed to be primarily composed of trehalose, was evident.Intracellular polyol was released during incubation of arthrospores obtained from media containing 25% or 10% glucose, in distilled water at 25° C, but no polyol was released under these conditions from arthrospores obtained from growth in 2% glucose medium.     

Effect of nitrate concentration on growth and pigment synthesis of Dunaliella salina cultivated under low illumination and preadapted to different salinities

A wild strain of Dunaliella salina was isolated from a solar evaporation salt-pond in Araya (Estado Sucre, Venezuela) and grown in batch culture using relatively low illumination (80 μmol photon m-2 s-1). After the alga had been adapted to various salinities (9, 14, 21% w/v NaCl), the influence of nitrate concentration (882, 435, 212 μmol L-1 N) on growth rate and chlorophyll a and total carotenoid concentrations was measured. Low nitrate concentration negatively affected growth, but enhanced carotenoid accumulation. A slight increase in carotenogenesis was also observed in alga grown at the highest salinity. There were no significant additive or synergistic effects of salinity and nutrient concentrations on the concentrations of chlorophyll a or total carotenoid. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fermentation of xylose and hemicellulose hydrolysates by an ethanol-adapted culture ofBacteroides polypragmatus

Bacteroides polypragmatus type strain GP4 was adapted to grow in the presence of 3.5% (w/v) ethanol by successive transfers into 1% (w/v)d-xylose media supplemented with increasing concentrations of ethanol. The maximum specific growth rate of the ethanol-adapted culture (=0.30 h^-1) was not affected by up to 2% (w/v) ethanol but that of the non-adapted strain declined by about 50%. The growth rate of both cultures was limited by nutrient(s) contained in yeast extract. The ethanol yield of the adapted culture (1.01 mol/mol xylose) was higher than that (0.80 mol/mol xylose) of the non-adapted strain. The adapted culture retained the ability to simultaneously ferment pentose and hexose sugars, and moreover it was not inhibited by xylose concentrations of 7–9% (w/v). This culture also readily fermented hemicellulose hydrolysates obtained by mild acid hydrolysis of either hydrogen fluoride treated or steam exploded Aspen wood. The ethanol yield from the fermentation of the hydrolysates was comparable to that obtained from xylose.This paper is issued as NRCC No. 26338     

Effects of Pluronic F-68 on callus growth and protoplast plating efficiency of Solanum dulcamara

Summary The effects of the non-ionic surfactant, Pluronic F-68, on the growth of callus and protoplasts from Solanum dulcamara L. have been studied. Growth of callus was stimulated by addition of 0.1% (w/v) commercial grade Pluronic to culture medium, whereas lower concentrations (0.01% w/v) had no corresponding effect. In contrast, higher concentrations (1.0% w/v) of Pluronic inhibited callus growth. The mean plating efficiency of protoplasts grown at different densities (15 days after plating) was increased up to 26% following culture with 0.1% (w/v) Pluronic, while 0.01% (w/v) Pluronic was ineffective. Mean protoplast plating efficiency decreased by up to 32% following culture with 1.0% (w/v) Pluronic.     

Effects of acetic acid and lactic acid on the growth of Saccharomyces cerevisiae in a minimal medium

Specific growth rates (μ) of two strains of Saccharomyces cerevisiae decreased exponentially (R ²>0.9) as the concentrations of acetic acid or lactic acid were increased in minimal media at 30°C. Moreover, the length of the lag phase of each growth curve (h) increased exponentially as increasing concentrations of acetic or lactic acid were added to the media. The minimum inhibitory concentration (MIC) of acetic acid for yeast growth was 0.6% w/v (100 mM) and that of lactic acid was 2.5% w/v (278 mM) for both strains of yeast. However, acetic acid at concentrations as low as 0.05–0.1% w/v and lactic acid at concentrations of 0.2–0.8% w/v begin to stress the yeasts as seen by reduced growth rates and decreased rates of glucose consumption and ethanol production as the concentration of acetic or lactic acid in the media was raised. In the presence of increasing acetic acid, all the glucose in the medium was eventually consumed even though the rates of consumption differed. However, this was not observed in the presence of increasing lactic acid where glucose consumption was extremely protracted even at a concentration of 0.6% w/v (66 mM). A response surface central composite design was used to evaluate the interaction between acetic and lactic acids on the specific growth rate of both yeast strains at 30C. The data were analysed using the General Linear Models (GLM) procedure. From the analysis, the interaction between acetic acid and lactic acid was statistically significant (P≤0.001), i.e., the inhibitory effect of the two acids present together in a medium is highly synergistic. Journal of Industrial Microbiology & Biotechnology (2001) 26, 171–177. Received 06 June 2000/ Accepted in revised form 21 September 2000     

Calmodulin-like protein and the phospholipids of Mycobacterium smegmatis

When Mycobacterium smegmatis TMC1546 was grown at different concentrations of glucose supplemented to a synthetic medium already containing 2% v/v glycerol, the following changes were observed. Amount of calmodulin-like protein (CAMLP), total and individual phospholipids (PLs) namely phosphatidylethanolamine, cardiolipin, phosphatidylglycerol and phosphatidylinositol mannosides and total lipids and growth increased up to 5% w/v but decreased at higher concentrations of glucose (7.5% w/v and above). Cyclic AMP content of the whole cells decreased continuously with increase in glucose concentration in the medium. Incorporation of 32Pi into total phospholipids was inhibited by two calmodulin antagonists trifluoperazine and phenothiazine (50% at 40 microM) and the calcium-specific chelator ethylene glycol bis (beta-aminoethyl ether) N,N,N',N'-tetraacetate (EGTA) 35% at 2 mM. Total lipids, CAMLP and growth of this organism are also modulated in a similar way in response to the glucose concentration in the growth medium. Taking these observations together it is suggested that CAMLP has some effect on the metabolism of PLs.