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.     

Plasmid effects on secondary metabolite production by a streptomycete synthesizing an anthelmintic macrolide.

Transformation of the thermotolerant streptomycete, soil isolate S541, with plasmid cloning vectors of varying size, copy number, and parent replicon (derived from pIJ101, SCP2* and SLP1.2) depressed the biosynthesis of nemadectins (polyketide-derived secondary metabolites possessing anthelmintic activity). However, production of the chemically distinct 21-hydroxyl-oligomycin A, also produced by S541, was either unaffected or increased in plasmid-containing strains. A causal relationship between plasmid carriage and the changes in secondary metabolite yield was confirmed since cured strains were restored to normal production levels and their subsequent retransformation by plasmid DNA was followed by the same effects on nemadectin and oligomycin biosynthesis as before. All the plasmids tested were highly unstable in S541 and it was generally necessary to include an appropriate selective antibiotic (usually thiostrepton) in the growth medium. Thiostrepton was not responsible for the depressive effect, since this was also observed in plasmid-containing strains (i) when grown in antibiotic-free media and (ii) when alternative selective antibiotics such as neomycin were used. In addition, the plasmid-free strain produced both nemadectins and 21-hydroxyl-oligomycin A in the presence of sub-inhibitory levels of thiostrepton. The thiostrepton resistance gene, which was present on many of the plasmids tested, did not mediate the effect since plasmids carrying other selectable markers (pIJ58, neomycin, and pIJ355, viomycin) also depressed nemadectin but not 21-hydroxyl-oligomycin A production. No obvious recombination or integration events between S541 chromosomal DNA and any of the plasmids tested were revealed by DNA-DNA Southern hybridization.     

A new streptomycete and a new polyene antibiotic,acmycin

A new antifungal antibiotic named acmycin was isolated from a soil streptomycete. Detailed comparative taxonomic studies showed that the organism differed from three related species of streptomycetes. The organism was referred to asStreptomyces sp. AC₂. The isolated antibiotic appears to be of polyene nature.     

The effect of temperature on the growth and hydrogen production by Citrobacter intermedius

Summary Citrobacter intermedius was grown batchwise in a mineral salts medium with glucose as a carbon and energy source under anaerobic conditions and at different temperatures. The effect of temperature on the following parameters was studied: maximum specific growth rate, max, maximum rate of hydrogen gas production and maximum rate of total gas (H₂ + CO₂) production. Arrhenius plots were used to determine the activation energies associated with max and maximum rates of hydrogen gas production.     

Interactive effects of propionic acid and temperature on growth and ochratoxin a production byPenicillium aurantiogriseum

Propionate at concentrations up to 0.05% decreased at 25 °C the growth and sporulation ofPenicillum aurantiogrseum. The standard size of conidiogeneous structures (metulae, phialids) and conidia was diminished. The effect was more pronounced at a higher temperature (30°C). Inhibition of ochratoxin production by propionate was also demonstrated.     

Purification and characterization of a new peptide antibiotic produced by a thermotolerant Bacillus licheniformis strain

A Bacillus licheniformis strain, 189, isolated from a hot spring environment in the Azores, Portugal, strongly inhibited growth of Gram-positive bacteria. It produced a peptide antibiotic at 50 degrees C. The antibiotic was purified and biochemically characterized. It was highly resistant to several proteolytic enzymes. Additionally, it retained its antimicrobial activity after incubation at pH values between 3.5 and 8; it was thermostable, retaining about 85% and 20% of its activity after 6 h at 50 degrees C and 100 degrees C, respectively. Its molecular mass determined by mass spectrometry was 3249.7 Da.     

Rapid growth of a thermotolerant yeast on palm oil

A thermotolerant and rapidly-growing yeast for production of single cell protein from palm oil was isolated and identified as Candida tropicalis F129. The optimum temperature and pH for growth were 38°C and 6.0, respectively. The yeast grew with a high specific growth rate, of 0.92/h in 2% (v/v) palm oil medium, compared with other oil-assimilating yeasts or hydrocarbon-utilizing thermophilic yeasts. The overall cell yield was 1.01 g dry cells/g palm oil after 12 h.     

The effects of temperature on bacterial production in a dimictic eutrophic lake

Abstract The incorporation of [³H](methyl)thymidine into DNA by the planktonic heterotropic bacteria of Little Crooked Lake (Noble Country, IN) was determined at different incubation temperatures. The highest rates of thymidine incorporation generally occurred at temperatures exceeding the in situ temperature of the sample. The optimal temperature for thymidine incorporation ranged from 1.0–3.4 times the in situ temperature. As the summer of 1983 progressed, the optimal temperatures for thymidine incorporation by epilimnetic samples and the in situ temperatures converged. This trend was reversed as fall overturn was approached.     

SCP production by Chaetomium cellulolyticum,a new thermotolerant cellulolytic fungus

Chaetomium cellulolyticum, a newly isolated cellulolytic fungus, showed 50–100% faster growth rates and over 80% more final biomass-protein formation than Trichoderma viride, a well-known high cellulase-producing cellulolytic organism, when cultivated on Solka-floc (a purified, predominantly amorphorous form of cellulose) or partially delignified sawdust (consisting of a mixture of hardwoods) as the sole-carbon source in the fermentation media. However, in both cases, T. viride produced much higher quantities of free cellulases at faster rates and also degraded more substrate than C. cellulolyticum. It is concluded that the synthesis mechanisms and/or the nature of the cellulase complexes of the two types of organisms are quite different such that C. cellulolyticum is more optimal for single-cell protein (SCP) production, while T. viride is more optimal for the production of extracellular cellulases. It was also found that the amino acid composition of C. cellulolyticum is generally better than that of T. viride and compares favorably with those of the FAO reference protein, alfalfa, and soya meal. In addition, preliminary feeding trials on rats have shown no adverse effects of the SCP produced by C. cellulolyticum fermentations.     

The effects of argulosis-saprolehniasis on the growth and production ofCyprinus carpoi

Growth profiles of maleCyprinus carpio, 12 uninfected (healthy) and 12 infected with the crustaceanArgulus indicus and associated fungusSaprolegnia sp. are presented. The fish were maintained under controlled conditions and provided withad libitum food for 8 weeks. The instantaneous (G) and relative (h) rates of growth, and production (P) in uninfected carp (0.003 to 0.036 g.d^–1, 0.29 to 3.68%, 0.25 to 3.23 g respectively) were much higher than those of infected carp ( – 0.007 to 0.021 g.d^–1, 0.71 to 2.17%, 0.59 to 1.76 g). The condition factor (K) for uninfected carp was 4.5 to 4.8 compared to 2.6 to 3.0 for infected carp. During each of the 8 wk the weekly change in weight of infected carp was about 4% less than that of uninfected carp. These data show thatArgulus-Saprolegnia infections significantly suppress carp growth and indicate that comparative growth rates can be used as indicators of parasite stress.     

Some environmental factors affect growth and antibiotic production by the mycoparasite Coniothyrium minitans

The effects of temperature and pH on growth and antibiotic production by three isolates of Coniothyrium minitans (Conio, Contans and IVT1), known to produce the macrolide antibiotic macrosphelide A, were examined in modified Czapek Dox broth (MCD). Antibiotic production was determined by incorporating heated (60°C for 5 min) C. minitans spent culture filtrates of MCD (10%, v/v) into potato dextrose broth and assessing the ability of the filtrates to inhibit growth of S. sclerotiorum. All isolates grew over the temperature range of 10–30°C, with the optimum at approximately 15–20°C. Antibiotics were produced by all isolates at 10–30°C. Culture filtrates of MCD from all isolates incorporated into PDB inhibited growth of S. sclerotiorum by >50%, whereas there was a reduction in inhibition at 30°C for Conio and IVT1 but not Contans. All three isolates grew over the pH range of 3–7, with greater biomass production in buffered pH 3–5 than the unbuffered control (pH 4.8) media. Antibiotics were produced by all isolates at pH 3–5. Culture filtrates of MCD from all three isolates grown at pH 3–5 inhibited growth of S. sclerotiorum, with the greatest effect on inhibition observed at pH 3. There were no differences in growth inhibition between isolates at pH 3 and 4, but culture filtrates from Conio grown at pH 5 inhibited S. sclerotiorum more than those of IVT1 grown at the same pH. The significance of these results for biocontrol and optimizing antibiotic production by C. minitans is discussed.     

Effects of reduced oxygen on growth and antibiotic production inStreptomyces clavuligerus

Summary The effects of reduced oxygen on growth and antibiotic production were studied in batch cultures ofStreptomyces clavuligerus in defined media. Antibiotic levels were unaffected by reduced oxygen for the first 50 hours of fermentation. After growth ceased, antibiotic concentrations dropped by a factor of about three under reduced oxygen, while the antibiotic concentration was stable when air was used. This suggests that enzymes for hydrolyzing antibiotics may be regulated by the aeration conditions.     

Chitinase production by a newly isolated thermotolerant Paenibacillus sp. BISR-047

Chitinase is one of the important mycolytic enzymes with industrial significance, and is produced by a number of organisms, including bacteria. In this study, we describe isolation, characterization and media optimization for chitinase production from a newly isolated thermotolerant bacterial strain, BISR-047, isolated from desert soil and later identified as Paenibacillus sp. The production of extracellularly secreted chitinase by this strain was optimized by varying pH, temperature, incubation period, substrate concentrations, carbon and nitrogen source,etc. The maximum chitinase production was achieved at 45 °C with media containing (in g/l) chitin 2.0, yeast extract 1.5, glycerol 1.0, and ammonium sulphate 0.2 % (media pH 7.0). A three-fold increase in the chitinase production (712 IU/ml) was found at the optimized media conditions at 6 days of incubation. The enzyme showed activity at broad pH (3–10) and temperature (35–100 °C) ranges, with optimal activity displayed at pH 5.0 and 55 °C, respectively. The produced enzyme was found to be highly thermostable at higher temperatures, with a half-life of 4 h at 100 °C.     

Effects of cpxR on the growth characteristics and antibiotic production of Xenorhabdus nematophila

CpxR is a global response regulator that negatively influences the antimicrobial activities of Xenorhabdus nematophila. Herein, the wildtype and ΔcpxR mutant of X. nematophila were cultured in a 5-l and 70-l bioreactor. The kinetic analysis showed that ΔcpxR significantly increased the cell biomass and antibiotic activity. The maximum dry cell weight (DCW) and antibiotic activity of ΔcpxR were 20.77 ± 1.56 g L⁻¹ and 492.0 ± 31.2 U ml⁻¹ and increased by 17.28 and 97.33% compared to the wildtype respectively. Xenocoumacin 1 (Xcn1), a major antimicrobial compound, was increased 3.07-fold, but nematophin was decreased by 48.7%. In 70-l bioreactor, DCW was increased by 18.97%, while antibiotic activity and Xcn1 were decreased by 27.71% and 11.0% compared to that in 5-l bioreactor respectively. Notably, pH had remarkable effects on the cell biomass and antibiotic activity of ΔcpxR, where ΔcpxR was sensitive to alkaline pH conditions. The optimal cell growth and antibiotic activity of ΔcpxR occurred at pH 7.0, while Xcn1 was increased 5.45- and 3.87-fold relative to that at pH 5.5 and 8.5 respectively. These findings confirmed that ΔcpxR considerably increased the biomass of X. nematophila at a late stage of fermentation. In addition, ΔcpxR significantly promoted the biosynthesis of Xcns but decreased the production of nematophin.     

Effects of temperature on the growth of the thermotolerant methylotrophic bacillus sp. NCIB 12522 in chemostat culture

The effects of temperature on chemostat cultures of a thermotolerant, methylotrophic Bacillus ap. are reported. In spite of the relative fastidiousness of this bacterium, overall response to a range of growth temperatures is predictable. However, anomalous results with respect to biomass yield coefficients are evident, suggesting complex and extensive endogenous and exogenous activities under some growth conditions.