Effect of Medium Components on Bacteriocin Production by Lactobacillus Pentosus ST151BR,a Strain Isolated from Beer Produced by the Fermentation of Maize,Barley and Soy Flour

Lactobacillus pentosus ST151BR, isolated from home-brewed beer, produces a 3.0 kDa antibacterial peptide (bacteriocin ST151BR) active against Lactobacillus casei, Lactobacillus sakei, Pseudomonas aeruginosa, Enterococcus faecalis and Escherichia coli. Treatment with Proteinase K or Pronase resulted in loss of activity. Bacteriocin levels of 6400 AU/ml were recorded in MRSbb (De Man-Rogosa-Sharpe broth without Tween 80) at pH 5.5, 6.0 and 6.5. The same growth conditions at pH 4.5 yielded only 1600 AU/ml bacteriocin. Inclusion of Tween 80 in the growth medium reduced bacteriocin production by more than 50%. Growth in the presence of tryptone or tryptone plus meat extract stimulated bacteriocin production, whereas much lower activity was recorded when the bacteria were grown in the presence of meat extract, yeast extract, tryptone plus yeast extract, meat extract plus yeast extract, or a combination of tryptone, meat extract and yeast extract. MRSbb supplemented with maltose, lactose or mannose (2.0%, w/v) yielded bacteriocin levels of 6400 AU/ml. Sucrose or fructose at these concentrations reduced the activity by 50 and 75%, respectively. Growth in the presence of 4.0%(w/v) glucose resulted in 50% activity loss. Glycerol levels as low as 0.1%(w/v) repressed bacteriocin production. Addition of cyanocobalamin, ascorbic acid, thiamine and thioctic acid (1.0 mg/l) to the growth medium did not lead to an increase in bacteriocin production. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cadmium transport by a Cd2+-sensitive and a Cd2+-resistant strain of Bacillus subtilis

Cadmium uptake by a Cd2+-sensitive (1A1) and a Cd2+-resistant mutant (1A1r) strain of Bacillus subtilis was investigated. Uptake of 109Cd2+ was determined for cells of both strains grown in tryptone broth and in broth containing tryptone, yeast extract, and glucose (TYG). The extent of 109Cd2+ uptake by cells of 1A1r was less than by cells of 1A1 under both growth conditions. In both growth media, 109Cd2+ uptake by 1A1 cells demonstrated saturation kinetics and was energy dependent. In both TYG and tryptone broth, 109Cd2+ uptake by 1A1 cells was inhibited by the addition of unlabeled Mn2+. Although lower in magnitude, the kinetics of 109Cd2+ uptake by 1A1r cells were similar to those of 1A1 cells when grown in tryptone broth. However, no obvious saturation kinetics, energy dependence, temperature sensitivity, or inhibition of 109Cd2+ uptake by the addition of unlabeled Mn2+ was observed in 1A1r cells grown in TYG. Differential Mn2+ accumulation by 1A1r cells in TYG and tryptone broth correlated with differential 109Cd2+ uptake by 1A1r cells in these media.     

pH effects on 10 Streptomyces spp. growth and sporulation depend on nutrients

AIMS: Streptomycetes are regarded to prefer neutral to alkaline environmental pH, although they commonly occur at remarkably variable pH and nutritional conditions. Therefore, the dependence of 10 Streptomyces spp. pH tolerance on nutrients was determined. METHODS AND RESULTS: Ten environmental Streptomyces spp. were grown and sporulated between pH 4.0 and 11.5, at the interval of 1.5, on starch-casein-KNO(3), tryptone-yeast extract-glucose, glycerol-arginine and tryptone-soy agars, and three their modifications. On media with starch and casein; glucose, tryptone and yeast extract; tryptone and soy peptone; and glycerol-arginine and yeast extract strains grew over a broad pH range between 4.0-5.5 and 10.0-11.5. On glycerol-arginine and on medium with Na-propionate, NH(4)NO(3) and yeast extract, streptomycetes grew optimally at pH 7.0 and above. The high organic load enabled the growth over a wide pH range. The sporulation pH ranges followed those for growth. CONCLUSIONS: The high organic load enabled the growth over a wide pH range. The strain-specific differences in sporulation were greater than those caused by pH. The best medium for sporulation contained glucose and tryptone with minerals of glycerol-arginine agar at pH 5.5. SIGNIFICANCE AND IMPACT OF THE STUDY: The growth pH ranges, pH ranges for the optimal growth, and sporulation were strongly dependent on nutrients.     

The effect of culture medium and aeration on growth of Listeria monocytogenes at pH 4.5

Listeria monocytogenes multiplied at 20°C in medium adjusted to pH 4.5 with HCl, and the lag before growth was eliminated when the inoculum was grown to log phase in the same medium. In a tryptone soya medium with yeast extract and added glucose, growth at pH 4.5 was more rapid than in a tryptose phosphate medium, and this difference was greater in air than under nitrogen. The results show that the bacterium was capable of more rapid growth in air than under nitrogen at this pH and suggest that the tryptose phosphate medium was nutritionally limiting for growth.     

Enhanced Biosynthesis of Sulfide Oxidase by Arthrobacter Species Using Response Surface Methodology

Response surface methodology was used to develop a fermentation medium for the enhanced biosynthesis of a novel sulfide oxidase by Arthrobacter species strain FR‐3. The interactive effect of the medium components – such as glucose as the carbon source, and tryptone and yeast extract as the nitrogen source – was evaluated by a 2³‐factorial central composite statistical design. Glucose and yeast extract were found to be the more influential medium constituents compared to tryptone since they had lower coefficients of linear effect, P‐values (< 0.02). The optimal fermentation medium components for the enhanced production of sulfide oxidase were recorded as glucose (8.98 g/L), tryptone (10.62 g/L) and yeast extract (7.3 g/L). Optimization of the medium constituents increased the experimental enzyme yield by 54 % compared to the unoptimized medium. This is the first report on the overproduction of sulfide oxidase by using response surface methodology.     

An empirical model for describing the effects of nitrogen sources on nisin production

AIMS: A study on the effects of tryptone and yeast extract on nisin production by Lactococcus lactis was carried out using a second order rotatable factorial design. METHODS AND RESULTS: The results show that both ingredients increased nisin production, although a small decrease in nisin levels was noted at high tryptone concentrations. In view of the low vitamin content of tryptone, the amino acids present in both tryptone and yeast extract may be responsible for these observations. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The observed response suggests that maintaining tryptone concentrations in the centre of the domain and increasing the concentration of yeast extract would be ideal conditions for nisin production. However, when the economic aspects are considered, it appears that low concentrations of yeast extract and reasonably high concentrations of tryptone are optimal.     

Fermentation of sugar cane bagasse hemicellulosic hydrolysate and sugar mixtures to ethanol by recombinant Escherichia coli KO11

Escherichia coli KO11, carrying the ethanol pathway genes pdc (pyruvate decarboxylase) and adh (alcohol dehydrogenase) from Zymomonas mobilis integrated into its chromosome, has the ability to metabolize pentoses and hexoses to ethanol, both in synthetic medium and in hemicellulosic hydrolysates. In the fermentation of sugar mixtures simulating hemicellulose hydrolysate sugar composition (10.0 g of glucose/l and 40.0 g of xylose/l) and supplemented with tryptone and yeast extract, recombinant bacteria produced 24.58 g of ethanol/l, equivalent to 96.4% of the maximum theoretical yield. Corn steep powder (CSP), a byproduct of the corn starch-processing industry, was used to replace tryptone and yeast extract. At a concentration of 12.5 g/l, it was able to support the fermentation of glucose (80.0 g/l) to ethanol, with both ethanol yield and volumetric productivity comparable to those obtained with fermentation media containing tryptone and yeast extract. Hemicellulose hydrolysate of sugar cane bagasse supplemented with tryptone and yeast extract was also readily fermented to ethanol within 48 h, and ethanol yield achieved 91.5% of the theoretical maximum conversion efficiency. However, fermentation of bagasse hydrolysate supplemented with 12.5 g of CSP/l took twice as long to complete. This revised version was published online in November 2006 with corrections to the Cover Date.     

Development of improved media for axenic cultivation of Acanthamoeba culbertsoni, Singh and Das 1970

Several varieties of peptone supported growth of A. culbertsoni to different extents reaching a maximum cell density of 1-2 X 10(6)/ml. Proteose peptone and tryptone also yielded good growth when combined with thiamine and vitamin B12. A combination of proteose peptone with glucose, yeast extract and salts promoted excellent growth of A. culbertsoni with cell density reaching 1-2 X 10(7) cells/ml; tryptone and one of the indigenous peptones also yielded comparable growth when substituted for proteose peptone in this medium. Casamino acids also supported good growth of amoebae and requirement of yeast extract could be met by a combination of thiamine, vitamin B12 and biotin. Bacto peptone did not support good growth of this amoeba but supplementation of peptone with casamino acids or amino acid mixture improved the growth supporting capacity of the medium. Development of several media with or without glucose will aid in cultivation of A. culbertsoni, studies on its metabolism as well as screening of potential drugs.     

6种细菌菌数测定培养基的优化

考察平板计数琼脂(PCA)中不同来源的酵母浸粉对6种细菌总数测定的影响,并对培养基中酵母浸粉和胰蛋白胨的配比及含量进行了优化。优化后的培养基组分为胰蛋白胨3.0 g·L-1,酵母浸粉3.0 g·L-1,葡萄糖1.0 g·L-1,琼脂15.0 g·L-1。与市售平板计数琼脂相比,能检出的细菌总数提高6.9%。     

Trimethylamine oxide: a terminal electron acceptor in anaerobic respiration of bacteria.

Trimethylamine oxide (TMAO) stimulated both the anaerobic growth rate and the growth yield of Proteus NTHC 153. The molar growth yield from glucose and pyruvate in tryptone/yeast extract medium doubled in the presence of TMAO, and the organism grew anaerobically on the non-fermentable substrates L-lactate and formate when TMAO was added to the medium. We conclude that TMAO stimulated growth by serving as a terminal electron acceptor in an oxidative phosphorylation process.     

Comparison of combinations of diluents and media for enumerating Zygosaccharomyces rouxii in intermediate water activity foods

Combinations of five diluents (0.1% peptone, 40 and 50% glucose, and 18 and 26% glycerol) and three enumeration media (tryptone glucose yeast extract, dichloran 18% glycerol and malt extract yeast extract 50% glucose (MY50G) agars) were evaluated for recovering a xerotolerant yeast, Zygosaccharomyces rouxii , from foods with intermediate water activity ( a _w). Combinations of 40% ( a _w, 0.936) or 50% ( a _w 0.898) glucose diluent and MY50G agar ( a _w 0.890) were superior in recovering highest populations. The type of solute in the diluent, as well as a reduced a _w, influences efficiency of recovering viable cells.     

Isolation from soil and properties of the extreme thermophile Clostridium thermohydrosulfuricum.

Thirteen strains of a strict anaerobic, extreme thermophilic bacterium were isolated from soil samples of moderate temperature, from a sewage plant in Georgia, and from hot springs in Utah and Wyoming. They were identified as strains of Clostridium thermohydrosulfuricum. The guanosine + cytosine content (moles percent) was 37.6 (determined by buoyant density) and 34.1 (determined by melting temperature). All strains required a factor present in yeast extract or tryptone growth. Growth characteristics were as follows: a pH range of 5 to 9, with the optimum between 6.9 to 7.5, in a temperature range of 40 to 78 degrees C, with the optimum at 68 degrees C. The doubling time, when grown on glucose at temperature and pH optima, was 1.2 h. The main products of glucose fermentation were ethanol, lactate, acetate, CO2, and H2. The fermentation was inhibited by H2. Formation of spores occurred easily on glucose-agar medium or when cultures growing at temperatures above 65 degrees C were allowed to cool to temperature below 55 degrees C. C. thermohydrosulfuricum occurs widely distributed in the natural environment.     

Impact of nutritional supplements and monosaccharides on growth, oxalate accumulation, and culture pH by Sclerotinia sclerotiorum

Sclerotinia sclerotiorum D-E7 was studied to determine the impact of nutritional supplements and monosaccharides on growth, oxalate accumulation, and culture pH in broth media (initial pH c. 5). Cultures with 0.1% nutritional supplement (tryptone, yeast extract, or soytone) yielded minimal growth, 2-3 mM oxalate, and a final culture pH of 4.2-4.8. In contrast, cultures with 0.1% nutritional supplement and 25 mM glucose yielded significant growth, minimal oxalate (<1 mM), and a final culture pH of 2.8-3.7. Similar trends were observed when glucose in 0.1% soytone cultures was replaced with 25 mM d-mannose, l-arabinose, or d-xylose. With 1% soytone-25 mM glucose cultures, growth and oxalate accumulation ( approximately 21 mM) occurred with little change in initial pH. This was not the case with 1% soytone-250 mM glucose cultures; increased glucose levels resulted in a decrease in oxalate accumulation ( approximately 7 mM) and in final culture pH (3.4). Time-course studies with these cultures revealed that oxalate accumulation was suppressed during growth when the culture pH dropped to <4. Overall, these results indicate that (1) the decrease in external pH (i.e. acidification) was independent of oxalate accumulation and (2) acidification coupled to glucose-dependent growth regulated oxalate accumulation by Sclerotinia sclerotiorum.     

Effect of incubation media on the recovery of Escherichia coli K12 heated at 52 degrees C.

The exposure of exponentially grown Escherichia coli K12 to 52 degrees C for 30 min in Tris/Mg2+ buffer resulted in a considerable loss of viability when plated on tryptone agar. When such heated bacteria were held at 37 degrees C for 2 h in tryptone broth before plating on tryptone agar, there was a significant increase in viability. Thus, heat damage was repaired in tryptone broth but not on tryptone agar. Recovery was greater in tryptone broth than in synthetic medium. In tryptone broth, recA or polA mutants also recovered but a lex mutant did not. As a result of heating, the sensitivity of bacteria to ultraviolet radiation (u.v.), to mitomycin C and to plating on high salt medium was enhanced. After incubation for 2 h in tryptone broth at 37 degrees C, the bacteria regained their resistance to u.v. and mitomycin C and tolerance to high salt medium. Recovery of viability required RNA and protein synthesis, whereas recovery of u.v. resistance did not require protein synthesis. Heating for 30 min inhibited the release of acid-soluble material from DNA in all strains of E. coli used.     

Defined conditions for synthesis of Bacillus cereus enterotoxin by fermenter-grown cultures.

A strain of Bacillus cereus produced high levels of enterotoxin when grown in a semidefined medium in a laboratory scale fermenter. The optimum conditions for enterotoxin synthesis by cultures grown in this medium, which contained Casamino Acids and yeast extract, were found to be: inoculation of vigorously gorwing culture at the 1% level, addition of glucose at a concentration of 1%, control of culture pH at 8.0, incubation at 32 degrees C, use of a moderate stirring rate, and addition of air at low flow rates to minimize foaming. The enterotoxin yield in fermenter-grown cultures was approximately 20 to 50 times higher than the yield obtained in shake flask cultures.     

Defined conditions for synthesis of Bacillus cereus enterotoxin by fermenter-grown cultures.

A strain of Bacillus cereus produced high levels of enterotoxin when grown in a semidefined medium in a laboratory scale fermenter. The optimum conditions for enterotoxin synthesis by cultures grown in this medium, which contained Casamino Acids and yeast extract, were found to be: inoculation of vigorously gorwing culture at the 1% level, addition of glucose at a concentration of 1%, control of culture pH at 8.0, incubation at 32 degrees C, use of a moderate stirring rate, and addition of air at low flow rates to minimize foaming. The enterotoxin yield in fermenter-grown cultures was approximately 20 to 50 times higher than the yield obtained in shake flask cultures.     

Photolysis in a culture medium for Tetrahymena pyriformis

Considerable variability has been found in the yield of cells in batch cultures of Tetrahymena pyriformis grown axenically in 1% tryptone/0.05% yeast extract. This variability has been traced to the photolysis by visible light of the flavin mononucleotide and thiamine components of yeast extract.     

A comparison of factors affecting the production of two bacteriocins from lactic acid bacteria

The effect of tryptone, yeast extract, Tween 80 and initial pH on the production of enterocin 1146 and lactocin D, two bacteriocins produced by lactic acid bacteria, was studied in a basal buffered medium (tryptone-yeast extract-tween, TYT) using factorial experiments and empirical modelling. Production of enterocin 1146 was affected by pH, yeast extract and Tween 80 and to a lesser degree, by the initial pH of the medium. On the basis of the predictions of the models developed, three TYT media (TYT10, TYT11 and TYT30) were designed to maximize bacteriocin production while minimizing the amount of peptides in the medium. Growth and bacteriocin production by Enterococcus faecium DPC 1146 (enterocin 1146), Lactococcus lactis subsp. lactis biovar diacetylactis DPC 3286 (lactocin D) and Lact. lactis subsp. cremoris LMG2130 (lactococcin A) was compared in TYT media and seven other culture media (Elliker lactic broth, M17, M17 dialysate, MRS, tryptose phosphate, tryptone yeast extract broth, yeast glucose Lemco broth). Bacteriocin production in TYT media was comparable with that in M17 and MRS, which had a higher peptide content. TYT30 allowed good production of enterocin 1146 and lactocin D while TYT11 proved acceptable for all the strains tested.     

Optimizing conditions for the growth of Lactobacillus casei YIT 9018 in tryptone-yeast extract-glucose medium by using response surface methodology.

This study was undertaken to find optimum conditions of tryptone, yeast extract, glucose, Tween 80, and incubation temperature for the growth of Lactobacillus casei YIT 9018 and to assess the effects of these factors by use of response surface methodology. A central composite design was used as an experimental design for allocation of treatment combinations. A second-order polynomial regression model, which was used at first for analysis of the experiment, had a significant lack of fit. Therefore, cubic and quartic terms were incorporated into the regression model through variable selection procedures. Effects involving incubation temperature, yeast extract, glucose, and tryptone were significant, whereas the only significant effect involving Tween 80 was the interaction effect between temperature and Tween 80. It turned out that growth of L. casei YIT 9018 was most strongly affected by the incubation temperature. Estimated optimum conditions of the factors for growth of L. casei YIT 9018 are as follows: tryptone, 3.04%; yeast extract, 0.892%; glucose, 1.58%; Tween 80, 0%; incubation temperature, 35 degrees C.     

代谢工程改造野生耐酸酵母生产L-乳酸

以选育低pH条件下高产L-乳酸的酵母菌为目的,从自然样品中筛选分离得到一株能在pH 2.5 (乳酸调节) 的培养基中生长且不利用乳酸的酵母 (初步鉴定为木兰假丝酵母Candida magnolia);进一步将来源于米根霉As3.819的乳酸脱氢酶编码基因 (ldhA) 插入含有G418抗性基因的酵母穿梭载体,构建了重组质粒pYX212-kanMX-ldhA,电转化入野生型C. magnolia中,筛选获得了一株具有产L-乳酸能力的重组菌株C. magnolia-2;通过发酵实验表明,该重组菌产L-乳酸的最