Influence of temperature on solvents production from whey

Summary The influence of temperature on solvent production from whey was investigated by using strains ofClostridium acetobutylicum andbutylicum. Higher yields of solvents were observed at 37°C or at 30°C depending on the strain used.     

Production of dextranase byLipomyces starkeyi

Summary The optimal growth rate ofLipomyces starkeyi, with dextran as sole carbon source, was found within the pH range 2.5–4.0, and temperature between 25–30°C. This yeast was unable to grow above 33°C. Dextranase production optima paralleled growth optima, except at pH 2.5. Decrease in enzyme yield at this pH could not be attributed to poor yeast growth or enzyme stability.     

The effect of temperature on the kinetics of ethanol production by Saccharomyces uvarum

Summary In view of the interest in high productivity fermentations at increased temperatures, the effect of temperature on the kinetics of ethanol production by Saccharomyces uvarum was investigated in the range 25–43°C. Using a mathematical model and a nonlinear computer simulation package, the kinetic parameters at each temperature were estimated. It was found that the optimal temperature for growth was 34°C, while the specific ethanol production rate was maximal at 37–43°C. Up to 37°C, the inhibitory effects of ethanol on growth and specific ethanol production rate were unaffected by temperature. However, above this temperature, ethanol inhibition increased significantly.     

The effect of temperature,pH, and initial glucose concentration on the kinetics of ethanol production by Zymomonas mobilis in batch fermentation

Summary Zymomonas mobilis, strain ATCC 10988, was used to evaluate the effects of pH (5.0 to 8.0), temperature (30°C to 40°C), and initial glucose concentration (75 g/l to 150 g/l) on the kinetics of ethanol production from glucose using batch fermentation. Specific ethanol production rate was maximum and nearly constant over a pH range of 6.0 to 7.5. End-of-batch ethanol yield and specific growth rate were insensitive to pH in the range of 5.0 to 7.5. End-of-batch ethanol yield was maximum and nearly constant between 30°C and 37°C but decreased by 24% between 37°C and 40°C. All other kinetic parameters are greatest at 34°C. End-of-batch ethanol yield is maximum at an initial glucose concentration of 100 g/l. Specific growth rate reaches a maximum at 75 g/l, but specific ethanol production rate decreases throughout the range. The optimum initial glucose concentration of 100 g/l gives the highest ethanol yield at a specific ethanol production rate less than 10% below the maximum observed.     

Production of cloned carboxypeptidase G2 by Escherichia coli: Genetic and environmental considerations

Summary The optimum production of cloned carboxypeptidase G₂ from plasmid pNM21 byEscherichia coli was found to be strongly strain- and temperature-dependent. The superior host was strain RV308 and the preferred growth temperature 28°C. Copy number, which decreased during exponential growth of all strains examined, did not relate in these studies to the level of enzyme production: the strain with the highest enzyme yield also having the lowest overall copy number.     

Ethanol production by zymomonas mobilis: Effect of temperature on cell growth,ethanol production and intracellular ethanol accumulation

Summary The kinetic behaviour of Zymomonas mobilis is studied at temperatures from 27 °C to 34.5 °C. Increases of temperature (above a critical value) have a negative effect on the yield of ethanol, mainly by raising the maintenance coefficient. Cell growth is less inhibited by the ethanol accumulation inside the cell than is the fermentative pathway. The specific rate of ethanol production is depressed when the intracellular ethanol concentration is maximal. An increase of temperature enhances this phenomenon.     

Production of acetone - butanol from acid whey

Summary Clostridium acetobutylicum ATCC 824 was used to produce butanol and acetone by fermenting acid whey. Results showed that both autoclaving and agitation played roles in solvent production. Maximum production was obtained in 120 h using autoclaved, pH adjusted (6.0) acid whey at 37 °C in a fermentor that was not agitated.     

Partial purification and characterization of a NADPH dependent tetrahydroalstonine synthase from Catharanthus roseus cell suspension cultures

A new enzyme was discovered which specifically hydrogenates the iminium form of cathenamine at position 21 to yield the heteroyohimbine alkaloid tetrahydroalstonine. The enzyme was partially purified (35-fold) from Catharanthus roseus cell suspension cultures. It was shown to use exclusively NADPH as reductant, the pH optimum is at 6.6, the temperature optimum at 30°C, the half life of the soluble enzyme preparation is 26 min at 37°C, and the molecular weight is 81 000 ± 3%. Evidence is presented for the occurrence of two distinct and different cathenamine reductases, one reducing the iminium form of this central intermediate to give tetrahydroalstonine, the other one reducing cathenamine to yield ajmalicine. Tetrahydroalstonine synthase was present in cell suspension cultures of C. ovalis, C. roseus, Picralima nitida, Rhazya stricta, and Vinca herbacea. Dedicated to Prof. Dr. Franz Lingens on the occasion of his 60th birthday     

Effect of temperature on plasmid stability and expression of cloned cellulase gene in a recombinantBacillus megaterium

Summary The expression of carboxymethyl cellulase gene inBacillus megaterium (pCK108) was investigated with respect to temperature in batch culture. The suboptimal temperature supporting maximal cell growth rate was determined to be 30 °C at which stability of the plasmid pCK108 could be maintained stable. However, cellular plasmid contents, production rate of cellulase of the cell, and efficiency of the gene expression increased significantly with increase of the temperature from 30 °C to 44 °C, even though the plasmid stability decreased up to 60% level at the end of the culture.     

Continuous culture of a recombinantEscherichia coli and plasmid maintenance for tryptophan production

Summary Production of tryptophan by a temperature sensitive recombinant microorganism (Escherichia coli W3110 trpLDtrpR ^ts tna ^– (pCRT185)) was investigated. In a single-stage continous culture, at an elevated temperature, 42°C (derepressed condition), tryptophan concentration increased in an early phase of the fermentation, and then gradually decreased with time. The reduction in the production rate was mostly due to the segregation of the plasmid and subsequent increase of plasmid-free cells. However, the plasmid could be maintained stable at 37°C, with repressed condition oftrp-operon, over 200 generations. A two-stage continuous culture system, i.e. cell growth was maintained in the first stage at 37°C and gene expression was induced in the second stage at 42°C, was therefore tested to improve the performance of the fermentation system. Operation of the two-stage system showed that the plasmid stability was significantly improved, and the specific rate of tryptophan production was maintained almost constant for more than 500 hours in the second stage.     

Effect of temperature on sucrose to ethanol conversion by Zymomonas mobilis strains

Summary Two strains of Zymomonas mobilis were tested for their ability to ferment sucrose to ethanol at elevated temperatures (30–42.5°C). The optimal temperature for efficient sucrose to ethanol conversion was 35°C with 22–27 h fermentation time and 75% conversion efficiency. Increases in magnesium concentration improved one of the strains at 40°C from 38 to 76% ethanol yield efficiency.     

The effect of temperature on the ethanol tolerance of the yeast,Saccharomyces uvarum

The optimum temperature for fermentation by Saccharomyces uvarum was found to be higher than that for its growth. Fermentation continued at temperatures above the growth maximum (40°C). S.uvarum was most resistant to growth inhibition by ethanol at temperatures 5°C and 10°C below its growth optimum (35°C). Fermentation became more resistant to ethanol inhibition with increasing temperature.     

The effect of temperature on the kinetics of ethanol production by strains of Zymomonas mobilis

Summary Two strains of Z. mobilis were evaluated for temperature sensitivity between 25°C and 40°C. At higher temperatures the cell viability, biomass yield, ethanol yield and final ethanol concentration decreased, and there was evidence of increased ethanol inhibition. However the kinetic parameters , q_s and q_p were largely unaffected by temperature over this range.     

By-products formed during direct conversion of sugar beets to ethanol byZymomonas mobilis in conventional submerged and solid-state fermentations

Summary The nature and amounts of by-products formed during conversion of sugar beets to ethanol byZ. mobilis in Conventional Submerged Fermentation (CSF) and Solid-State Fermentation (SSF) were investigated. It was found that the bacterium produced fewer by-products in SSF than CSF, and that by-products profile was different. The influence of fermentation temperature on synthesis of by-products in SSF was also studied. High fermentation temperature favoured sorbitol synthesis and low fermentation temperature the synthesis of levan. The best results were obtained at 35°C. An ethanol yield of up to 95% of the theoretical value with final ethanol concentration of 142 g/L were obtained.     

The isomaltulose synthesising enzyme ofSerratia plymuthica

Summary An intracellular enzyme was located inSerratia plymuthica which produced isomaltulose from sucrose. The enzyme was purified giving a preparation with a specific activity of 1,285. It has pH and temperature optima of 6.0 and 30°C, respectively. The enzyme was stable retaining 100% activity after 2 weeks at 30°C. It had an isoelectric point at pH 9.0, a Mr of 79,500 and the Km for sucrose was 65.3mM. The enzyme converted 40% (w/v) sucrose to isomaltulose with an efficiency of 87%.     

Studies on the alkalophilicStreptomyces with extracellular xylanolytic activity

Summary An alkalophilicStreptomyces which produced xylanase, isolated from soil, grew in a temperature range of 15–37°C. The pH optimum for growth was 10 and no growth occurred at pH 7. On a simple wheat bran medium the microorganism exhibited maximum enzyme secretion of 12 U/ml at pH 10. The enzyme had a broad pH optimum of 4.8–10 and the optimum temperature of 50°C. It was completely inactivated at 60°C in 2 h. The enzyme hydrolyzed xylan to a mixture of oligomeric products indicating that the main activity was of the endoxylanase type. The culture filtrate had no cellulase activity.     

A constitutive endoglucanase (CMCase) from Bacillus licheniformis-1

Summary Bacillus licheniformis-1 elaborated a constitutive extracellular CMCase. The temperature and pH optima of the enzyme were 55°C and 6.1 respectively. Its production was enhanced in the presence of easily metabolisable sugars and was lower when cellulosic sources were used.Abbreviations used CMC Carboxy Methyl Cellulose. - CP-60 Cellulose Powder 60 - CP-100 Cellulose Powder 100 - CP-X Cellulose Powder X     

Production of active human interferon-β inE. coli I. Preferential production by lower culture temperature

Summary Unusually low culture temperature, such as 20°C, was shown to be preferable for the synthesis of active human interferon- (IFN-) inE. coli harboring a recombinant plasmid. TheE. coli cells cultured at 20°C gave 8.6-fold higher IFN- activity than those cultured at 37°C. However, almost the equal amounts of IFN- protein were accumulated in both cells cultured at 20°C and at temperature higher than 20°C, suggesting that IFN- might exist as an active form in the cells cultured at 20°C, while as a rather denatured form in the cells cultured at higher temperature.     

Physical factors influencing the production of strawberry aroma byPseudomonas fragi grown in skim milk

Summary The influence of temperature, agitation speed, pH and biomass on the synthesis of 19 metabolites contributing to a strawberry aroma was followed over a 72 h fermentation of skim milk byPseudomonas fragi. Amongst the major odor-active metabolites were ethyl butyrate, ethyl hexanoate, ethyl 2-hexenoate, ethyl crotonate, ethyl isovalerate and ethyl 2-methyl hexanoate. Up to 17 ppm of some of these metabolites were detected at 60 h of fermentation, approximately 36 h after the beginning of the stationary growth phase. The production of most odor-active metabolites was higher at 11°C and 150 RPM than at 15, 20 or 25°C and 200 or 250 RPM. The development of off-aromas was observed at high temperatures and at high agitation speeds.     

Studies on xylan degrading enzyme from Chainia

Summary The sclerotial actinomycete Chainia (NCL 82-5-1) secreted extracellular xylanase in submerged culture in media containing yeast extract and wheat bran or commercial xylan. A high activity (28 IU/ml) of xylanase was obtained in 72 h on a medium containing 3% xylan. Only a single species of xylanase (i.e. without isoenzymes) was detected by polyacrylamide gel electrophoresis. It had an optimum pH of 5.0 and optimum temperature of 65°C. It was stable at pH 6.0 to heating at 60°C for 10 min. Its pI was 8.0 and the K_m was 0.4%. The results are discussed in relation to xylanase reported from actinomycetes such as Streptomyces xylophagus.