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.     

Regulation of product synthesis in cell cultures of Catharanthus roseus. Effect of culture temperature

A three year old, alkaloid producing cell line of Catharanthus roseus, maintained at 25°C, was grown on 2% sucrose at various temperatures from 10° to 45°C. Growth rates were maximal at 35°C but declined rapidly above 35°C and below 25°C. Maximum serpentine yields reached a peak at between 20°C and 25°C and fell sharply above and below these temperatures, while ajmalicine showed a sharp peak of accumulation at 20°C. The variable serpentine/ajmalicine ratio at different growth temperatures suggests that lower temperatures may favour ajmalicine accumulation. Both the growth rate and the rate of alkaloid accumulation at 25°C were therefore sensitive to small changes in average culture temperature.     

The analysis of water in the Martian regolith

Summary One of the scientific objectives of the Viking Mission to Mars was to accomplish an analysis of water in the Martian regolith. The analytical scheme originally envisioned was severly compromised in the latter stages of the Lander instrument package design. Nevertheless, a crude soil water analysis was accomplished. Samples from each of the two widely separated sites yielded roughly 1 to 3% water by weight when heated successively to several temperatures up to 500°C. A significant portion of this water was released in the 200° to 350°C interval indicating the presence of mineral hydrates of relatively low thermal stability, a finding in keeping with the low temperatures generally prevailing on Mars. The presence of a duricrust at one of the Lander sites is taken as possible evidence for the presence of hygroscopic minerals on Mars. The demonstrated presence of atmospheric water vapor and thermodynamic calculations lead to the belief that adsorbed water could provide a relatively favorable environment for endolithic organisms on Mars similar to types recently discovered in the dry antarctic deserts.     

Production of ethanol at high temperatures in the fermentation of Jerusalem artichoke juice and a simple medium byKluyveromyces marxianus

Summary Temperatures as high as 36°C and 40°C did not negatively affect the ethanol productivity of Jerusalem artichoke (J.a.) juice batch fermentation and the final concentrations of ethanol were close to those produced at lower temperatures. At higher process temperatures (36–40°C), ethanol toxicity inKluyveromyces marxianus was less important during the fermentation of J.a. juice as compared with a simple medium. In simple medium, the heat-sticking of fermentation was observed and the percentage of unfermented sugars steeply increased from 28°C up to 40°C.     

The effect of temperature on the kinetics of ethanol production by a thermotolerant strain of Kluveromyces marxianus

Summary The batch fermentation kinetics of a novel thermotolerant strain of the yeast Kluveromyces marxianus were evaluated between 30°C and 48°C. The most significant effects of elevated temperature were reductions in overall biomass and ethanol yields. Decreases in the concentration of ethanol attained, and the presence of unutilized substrate suggested increased ethanol inhibition at the higher temperatures studied.     

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.     

Production and characterization of xylanase from Bacillus thermoalkalophilus grown on agricultural wastes

Summary Bacillus thermoalkalophilus isolated from termite-infested mound soils of the semi-arid zones of India had the ability to produce good amounts of xylanase(s) from cheap agricultural wastes. Of the two hemicellulosic substrates tested, bagasse was found to be the better inducer for xylanase production. Alkali treatment of bagasse and rice husk had varied effects on enzyme production. The enzyme preparation had activity optima at 60° C and 70° C and a half-life of 60 min at 65° C. The enzyme was stable for 24 h over a pH range of 4.0–6.0, while maximum activity was observed at pH 6.0–7.0. Enzyme production and activity were inhibited by the end-product of xylan hydrolysis, xylose. Offprint requests to: Ajit Varma     

Ethanol production from glucose byClostridium thermosaccharolyticum strains: Effect of pH and temperature

Summary The fermentation of glucose byClostridium thermosaccharolyticum strains IMG 2811^T, 6544 and 6564 was studied in batch culture in a complex medium at different temperatures in defined and free-floating pH conditions. All the strains ferment 5 g glucose.l^–1 completely. The yield of the fermentation products turned out to be independent of the incubation temperature for strain IMG 2811^T. Strain IMG 6544 produced at 60°C significantly more ethanol and less acetic acid, butyric acid, hydrogen gas and biomass than at lower temperatures. With strain IMG 6564, the opposite effect occurred: ethanol appeared to be the main fermentation product at 45°C; at 60°C less ethanol and more acetic acid, butyric acid and hydrogen gas was formed.Experiments, carried out with strain IMG 6564, at defined pH conditions (between 5.5 and 7) and different temperatures (45, 55 and 60°C) revealed no effect of the incubation temperature, but an important effect of the pH on the product formation. At pH 7, ethanol was the main fermentation product while minor amounts of hydrogen gas, acetic and butyric acid were produced. Lowering the pH gradually to 5.5 resulted in a decrease of ethanol and an increase of biomass, hydrogen gas, acetic, butyric and lactic acids. At pH higher than 7 no growth occurred. Similar conclusions could be drawn for strains IMG 2811^T and 6544.     

Seed survival in small myrtaceous capsules subjected to experimental heating

Mature capsules of four small-fruited Myrtaceae (Eucalyptus regnans, Leptospermum laevigatum, L. myrsinoides and Kunzea ambigua) were heated in a muffle furnace over a range of temperatures (200–750° C) and for various lengths of time (15–300s). In addition, the rise in intracapsular temperature with time was measured at 250° C and the lethal seed temperature for K. ambigua determined by heating loose seed in a controlled-temperature water bath. Encapsulated seed survived heating for only short periods event at the lower range of experimental temperatures, with no seed surviving for more than 2 min at 200° C and the highest temperature survived being 650° C for 15 s by L. laevigatum. The species were ranked E. regnans, K. ambigua, L. myrsinoides and L. laevigatum in increasing order of insulating capacity of their capsules, based on survival times of encapsulated seed and the rate of increase of intracapsular temperatures. Seed of K. ambigua was killed when heated in water for a few seconds at 90–100° C. This result agrees closely with the threshold lethal temperature derived for all species by superimposing seed survival versus time and intracapsular temperature versus time curves for capsules heated at 250° C. These results demonstrate that despite their in situ efficacy during fire, small myrtaceous capsules hre mediocre seed insulators. They also suggest that in the field, survival times for encapsulated seed are likely to be in the order of seconds rather than minutes, which points to brief flame residence times in individual tree or shrub canopies. This work has the potential to be developed as a simple but powerful method for the measurement and mapping of fire intensities.     

Effect of hot-water extraction on alkaline pulping of bagasse

The effect of hot-water extraction on alkaline pulping was investigated. The properties of black liquor and pulp strength of bagasse were analyzed. The extraction was conducted at 160 °C for 30 min where 13.2% of the mass was dissolved in the extraction liquor. Untreated bagasse and extracted bagasse were digested by soda and soda-AQ processes at 17% and 15.5% (with 0.1% AQ) alkali charge (NaOH). Cooking temperatures were 160 °C and 155 °C respectively. The pulp from extracted bagasse had a lower Kappa number and a higher viscosity compared to the pulp from the untreated bagasse. The black liquor from pulping extracted bagasse had a lower solid content, a lower viscosity and a lower silica content, but a higher heating value than that from pulping of untreated bagasse. Hot-water extraction resulted in a significant decrease in bleaching chemical consumption and the formation of chlorinated organics. Pulp strength properties such as the tensile index and the burst index were found to be lower, but the tear index, bulk, opacity and pulp freeness were found to be higher when hot-water extraction was applied.     

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.     

Preparation of levoglucosenone through sulfuric acid promoted pyrolysis of bagasse at low temperature

Fast pyrolysis of bagasse pretreated by sulfuric acid was conducted in a fixed bed reactor to prepare levoglucosenone (LGO), a very important anhydrosugar for organic synthesis. The liquid yield and LGO yield were studied at temperatures from 240 to 350 °C and sulfuric acid loadings from 0.92 to 7.10 wt.%. An optimal LGO yield of 7.58 wt.% was obtained at 270 °C with a sulfuric acid pretreatment concentration of 0.05 M (corresponding to 4.28 wt.% sulfuric acid loading). For comparison, microcrystalline cellulose pretreated by 0.05 M sulfuric acid solution was pyrolyzed at temperature from 270 °C to 320 °C, and bagasse loaded with 3-5 wt.% phosphoric acid was pyrolyzed at temperature from 270 °C to 350 °C. The highest yield of LGO from bagasse was 30% higher than that from microcrystalline cellulose, and treatment with sulfuric acid allowed a 21% higher yield than treatment with phosphoric acid.     

A new perspective on thermal inactivation kinetics of human serum butyrylcholinesterase

Butyrylcholinesterase purified from human serum as 6600-fold was heated at 37°, 40°, 45°, and 50°C for 24 hr. It was observed that the enzyme heated at 45°C for 24 hr converted to a stabilized form and followed Michaelis-Menten kinetics, whereas the enzyme samples, heated at the other temperatures for 24 hr, shown negative cooperativity with respect to its substrate, butyrylthiocholine. Even the sample heated at 45°C for 12 hr shown negative cooperativity. On the contrary to the heated enzyme at 40°C for 24 hr, the heated enzyme at 45°C for 24 hr could not be reactivated when it was kept at 4°C for 24 hr. In the kinetic studies, it was found that substrate analogs choline and benzoylcholine inhibited both the native enzyme and the enzyme heated at 45°C for 24 hr competitively, whereas succinylcholine was the partial competitive inhibitor of native enzyme but the pure competitive inhibitor of the heated enzyme.     

Changes in heated and autoclaved forest soils of S.E. Australia. II. Phosphorus and phosphatase activity

The effect of soil heat and autoclaving on labile inorganic P (Bray I), microbial P (P-flush) and on phosphatase activity was studied by heating five forest soils in the laboratory, which simulated the effects of heat during bushfires. Top soil was heated to 60 °C, 120 °C and 250 °C or autoclaved for 30 minutes. Soils were analysed immediately after heating and during seven months of incubation to assess immediate and longer-term effects of heating.Labile inorganic P increased immediately after heating and autoclaving soils, with the highest amount recorded for the 250 °C treatment. Phosphorus associated with microbial biomass decreased with heat, and none or small amounts were detected in soils heated to 250 °C and autoclaved, because high temperatures killed the microbial population. Most of the P released from microbes acted as a source of labile inorganic P in soils low in inorganic P, and some of the released P was fixed by the soil. In one soil high in inorganic labile P and with undetectable amounts of microbial-P, the increase in Bray P on heating could only be assigned to solubilisation of other sources of total P Because high temperatures denature enzymatic proteins, phosphatase activity diminished with the increase in temperature, and no activity was detected in 250 °C and autoclaved soils.Phosphorus released by heating decreased during incubation in three of the five soils studied, approaching values observed in unheated soils. Simultaneously, an increase in microbial P was observed in these heated soils, indicating that the partial recovery of microbial biomass acted as a sink for the decrease in Bray-P measured. Phosphatase activity recovered only partially during incubation of heated soils.     

Delignification of sugarcane bagasse using glycerol-water mixtures to produce pulps for saccharification

This paper describes the organosolv delignification of depithed bagasse using glycerol–water mixtures without a catalyst. The experiments were performed using two separate experimental designs. In the first experiment, two temperatures (150 and 190 °C), two time periods (60 and 240 min) and two glycerol contents (20% and 80%, v/v) were used. In the second experiment, which was a central composite design, the glycerol content was maintained at 80%, and a range of temperatures (141.7–198.3 °C) and time (23–277 min) was used. The best result, obtained with a glycerol content of 80%, a reaction time of 150 min and a temperature of 198.3 °C, produced pulps with 54.4% pulp yield, 7.75% residual lignin, 81.4% delignification and 13.7% polyose content. The results showed that high contents of glycerol tend to produce pulps with higher delignification and higher polyoses content in relation to the pulps obtained from low glycerol content reactions. In addition, the proposed method shows potential as a pretreatment for cellulose saccharification.     

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.     

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.     

Translocation blockage by sieve plate callose

Summary Axial translocation in 2-week-old cotton plants was inhibited by heating 4 cm of intact hypocotyl for 15 min by means of a 40–45° water jacket. A 1-cm jacket did not retard translocation, and temperatures below 40° had no effect. Translocation continued to be inhibited for at least 3 hours following heat treatment. After 6 hours, rates were equal to or above normal. Maximum amounts of callose were deposited on sieve plates after the heat treatment, but callose was noticeably diminished within 6 hours after heating and reduced to virtually normal levels within 2 days. Growth measurements, plasmolytic tests, vital staining, and visual observations revealed no evidence of injury in plants heated at 45°. Pore constriction from increased amounts of callose on sieve plates appears to be an effect of heating. Increased resistance due to such constriction may be an important factor in blockage of basipetal phloem translocation.Work supported in part by National Science Foundation Grant GB-2941. This material is abstracted from a dissertation presented in 1967 by R. B. McNairn to the Graduate Division, University of California at Davis in partial fulfillment of the requirements for the Ph. D. degree.All temperatures in this paper are in degrees centigrade (°C)     

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.