Influence of growth conditions on the production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from kimchi

The influence of growth parameters on the fermentative production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from kimchi was studied. The bacteriocin production was greatly affected by carbon and nitrogen sources. Strain A164 produced at least 4-fold greater bacteriocin in M17 broth supplemented with lactose than other carbon sources. The amount of 3% yeast extract was found to be the optimal organic nitrogen source. While the maximum biomass was obtained at 37 degrees C, the optimal temperature for the bacteriocin production was 30 degrees C. The bacteriocin production was also affected by pH of the culture broth. The optimal pH for growth and bacteriocin production was 6.0. Although the cell growth at pH 6.0 was nearly the same level at pH 5.5 and 6.5, the greater bacteriocin activity was observed at pH 6.0. Exponential growth took place only during an initial period of the cultivation, and then linear growth was observed. Linear growth rates increased from 0.160 g(DCW) x l(-1) x h(-1) to 0.245 g(DCW) x l(-1) x h(-1) with increases in lactose concentrations from 0.5 to 3.0%. Maximum biomass was also increased from 1.88 g(DCW) x l(-1) to 4.29 g(DCW) x l(-1). However, increase in lactose concentration did not prolong the active growth phase. After 20 h cultivation, cell growth stopped regardless of lactose concentration. Production of the bacteriocin showed primary metabolic kinetics. However, bacteriocin yield based on cell mass increased greatly during the late growth phase. A maximum activity of 131x10(3) AU x ml(-1) was obtained at early stationary growth phase (20 h) during the batch fermentation in M17L broth (3.0% lactose) at 30 degrees C and pH 6.0.     

枯草芽孢杆菌中性β—甘露聚糖酶的产生及性质

由土壤中分离出一株产中性β甘露聚糖酶的枯草芽孢杆菌（Ｂａｃｉｌｕｓｓｕｂｔｉｌｉｓ）,编号ＢＭ９６０２。该菌在液体培养条件下,产生中性β甘露聚糖酶。多糖能作为碳源,而单糖不能作为碳源;有机氮源优于无机氮源。产酶最适培养基组成：魔芋粉４％,牛肉蛋白胨和酵母膏各１％。产酶最适培养条件：培养基起始ｐＨ８５,３５℃,振荡培养３６ｈ。以槐豆胶为底物,培养滤液中性β甘露聚糖酶活力为９６ＩＵ／ｍＬ。酶在ｐＨ５０～１００和５０℃下稳定;作用最适条件为ｐＨ６０和５０℃;水解魔芋粉和槐豆胶均产生寡聚糖。     

Incorporation and accumulation of docosahexaenoic acid from the medium by Pichia methanolica HA-32

Yeast species were screened for the incorporation and accumulation of docosahexaenoic acid (DHA) with a yeast-malt medium containing 0.5% free fatty acid prepared from fish oil (DHA, 28% of total fatty acids in fish oil). The most suitable strain was Pichia methanolica HA-32. The optimum cultivation conditions for the accumulation of lipids and incorporation of DHA were as follows: 5% glucose, 20% yeast extract, and 3% free fatty acid in the medium, at pH 6.0 and with incubated at 25 degrees C for 3 days. Under these conditions, about 200 mg of total lipids and 60 mg of DHA were recovered from 1 g of dry cells. The accumulation of DHA in cells increased in conjunction with the amount of yeast extract added to the medium. Vitamin B groups and minerals also had an effect on the accumulation of DHA. Choline and K2HPO4, which caused browning of the medium, promoted the accumulation of DHA in cells.     

Incorporation and Accumulation of Docosahexaenoic Acid from the Medium by Pichia methanolica HA-32

Yeast species were screened for the incorporation and accumulation of docosahexaenoic acid (DHA) with a yeast-malt medium containing 0.5% free fatty acid prepared from fish oil (DHA, 28% of total fatty acids in fish oil). The most suitable strain was Pichia methanolica HA-32. The optimum cultivation conditions for the accumulation of lipids and incorporation of DHA were as follows: 5% glucose, 20% yeast extract, and 3% free fatty acid in the medium, at pH 6.0 and with incubated at 25°C for 3 days. Under these conditions, about 200 mg of total lipids and 60 mg of DHA were recovered from 1 g of dry cells. The accumulation of DHA in cells increased in conjunction with the amount of yeast extract added to the medium. Vitamin B groups and minerals also had an effect on the accumulation of DHA. Choline and K₂HPO₄, which caused browning of the medium, promoted the accumulation of DHA in cells.     

Statistical media optimization for the biomass production of postharvest biocontrol yeast Rhodosporidium paludigenum

A cane molasses-based medium for the biomass production of biocontrol agent Rhodosporidium paludigenum was statistically optimized. Molasses concentration (after pretreatment), yeast extract, and initial pH were identified by the Plackett-Burman design to show significant influence on the biomass production. The three factors were further optimized by central composite design and response-surface methodology. The statistical analysis indicated the optimum values of the variables were 89.98?g/L for cane molasses, 2.35?g/L for yeast extract and an initial pH of 8.48. The biomass yield at the optimal culture achieved 15.89?g/L in flask fermentation, which was 2.1 times higher than that at the initial NYDB medium. In a 10-L fermenter, 18.97?g/L of biomass was obtained after 36?hr of cultivation. Moreover, the biocontrol efficacy of the yeast was investigated after culture optimization. The results showed the yeast harvested in the optimal medium maintained its initial biocontrol properties by reducing the percentage of decayed apples to below 20%.     

STATISTICAL MEDIA OPTIMIZATION FOR THE BIOMASS PRODUCTION OF POSTHARVEST BIOCONTROL YEAST Rhodosporidium paludigenum

A cane molasses-based medium for the biomass production of biocontrol agent Rhodosporidium paludigenum was statistically optimized. Molasses concentration (after pretreatment), yeast extract, and initial pH were identified by the Plackett–Burman design to show significant influence on the biomass production. The three factors were further optimized by central composite design and response-surface methodology. The statistical analysis indicated the optimum values of the variables were 89.98 g/L for cane molasses, 2.35 g/L for yeast extract and an initial pH of 8.48. The biomass yield at the optimal culture achieved 15.89 g/L in flask fermentation, which was 2.1 times higher than that at the initial NYDB medium. In a 10-L fermenter, 18.97 g/L of biomass was obtained after 36 hr of cultivation. Moreover, the biocontrol efficacy of the yeast was investigated after culture optimization. The results showed the yeast harvested in the optimal medium maintained its initial biocontrol properties by reducing the percentage of decayed apples to below 20%.     

一步法发酵菊芋产乙醇菌种的筛选及产酶条件、酶学性质的研究

从腐烂的菊芋及实验室保存的菌种中,选育到一株发酵菊芋产乙醇的菌株克鲁维酵母Kluyveromyces marxianus Y1。利用正交实验法对克鲁维酵母产菊粉酶的培养基组成及培养条件进行优化,确定培养基组成（g/L）为：菊粉40,酵母粉4,蛋白胨4,尿素1;初始pH5．0,温度30℃,150r／min条件下培养达到最佳产酶效果（57U／mL）。该菌株所产菊粉酶的性质测定结果表明：以菊粉为底物,该菊粉酶最适反应温度为55℃,在60℃以下稳定性很好,高于60℃时酶迅速失活;最适pH为5．0,pH4．6—5．2范围内酶稳定性很好;该酶属于外切型菊粉酶,体积分数为8％的乙醇对酶活力基本没有影响。     

A survey of yeast ureases and characterisation of partially purified Rhodosporidium paludigenum urease

Cell-free extracts of a selection of yeasts were analysed for urease activity. Species in the genera Filobasidiella, Rhodotorula and Rhodosporidium had the highest specific activities. Immune inactivation experiments showed widely different degrees of cross-reactivity between antiserum to jack bean urease and yeast ureases, with Rhodosporidium paludigenum (71%) the most and Schizosaccharomyces pombe (3%) the least affected. Only R. paludigenum urease was detected with anti-jack bean urease antiserum on Western blots. The urease of Rhodosporidium paludigenum was partially purified by column chromatography. The native enzyme was found to have a subunit size of 72 +/- 7 kDa probably in an octamer arrangement of 560 +/- 8 kDa, having a specific activity of 62.5 mumol urea hydrolysed min-1 (mg protein)-1. The enzyme was stable in the pH range 5-11 with optimum activity at pH 7.8. Vmax and Km values were determined as 65.2 +/- 3.8 mumol min-1 (mg protein)-1 and 3.81 +/- 0.47 mM, respectively.     

Dextransucrase production using cashew apple juice as substrate: effect of phosphate and yeast extract addition

Cashew apples are considered agriculture excess in the Brazilian Northeast because cashew trees are cultivated primarily with the aim of cashew nut production. In this work, the use of cashew apple juice as a substrate for Leuconostoc mesenteroides cultivation was investigated. The effect of yeast extract and phosphate addition was evaluated using factorial planning tools. Both phosphate and yeast extract addition were significant factors for biomass growth, but had no significant effect on maximum enzyme activity. The enzyme activities found in cashew apple juice assays were at least 3.5 times higher than the activity found in the synthetic medium. Assays with pH control (pH = 6.5) were also carried out. The pH-controlled fermentation enhanced biomass growth, but decreased the enzyme activity. Crude enzyme free of cells produced using cashew apple juice was stable for 16 h at 30°C at a pH of 5.0.     

Combined effects of pH, yeast extract, carbohydrates and di-ammonium hydrogen citrate on the biomass production and acidifying ability of a probiotic Lactobacillus plantarum strain, isolated from table olives, in a batch system

A four variables-five levels Central Composite Design (CCD) was developed to model the individual and interactive effects of carbohydrates (lactose or maltose), yeast extract, di-ammonium hydrogen citrate and pH on the biomass production (Abs_600 nm), viable and cultivable cell number and acidifying ability of a probiotic strain of Lactobacillus plantarum, isolated from table olives “Bella di Cerignola”. pH values were modeled through a negative Gompertz equation, in order to obtain the parameter α (metabolic adaptation time). This value and the biomass were submitted to a stepwise procedure and second order polynomial equations were derived. The parameter α was affected by the initial pH and lactose; the effect of the maltose, however, was not significant. The biomass production increased with increasing of yeast extract, di-ammonium hydrogen citrate and maltose concentrations and was maximum at pH 6.0 and 20 g l⁻¹ of lactose.     

Effect of ethanesulfonic acid buffers and pH on the accumulation of a nervous system-specific protein (S-100) and a glial-enriched enzyme in a clonal line of rat astrocytes (C6).

Stationary phase cultures of a clonal line of rat astrocytes (C6) were maintained at pH values ranging from 6.0 to 8.4 using media buffered with various combinations of organic buffers or graded concentrations of bicarbonate ion at a constant CO2 tension. The accumulation of a soluble acidic protein unique to the nervous system (S-100) in media buffered with organic buffers was optimal in the pH range 6.4 to 6.8, significantly more acid than that optimal for cell growth (pH 7.0 to 7.8). Cells maintained in CO2-bicarbonate-buffered media exhibited a higher and less marked pH optimum for S-100 protein accumulation and a lower efficiency of accumulation of the protein. These data suggest that the organic buffer ions themselves, apart from their function as buffers, are influencing the accumulation of S-100. The specific activity (assayed at the enzymatic pH optimum) of a membrane-bound enzyme enriched in glial cells and myelin, 2',3'-cyclic nucleotide 3'-phosphohydrolase, was markedly pH-dependent. The optimal pH range was 6.4 to 6.7 in organic buffer controlled media. In CO2-bicarbonate controlled media the optimal pH range was only slightly higher (pH 6.6 to 7.0), but the specific activities were reduced relative to organic buffer-grown cells. The structural relationship of some of the aminoethanesulfonic acid buffers used in these experiments to certain compounds of neurochemical interest (such as taurine and alpha-flupenthixol) is noted.     

Sequence-directed DNA Curvature in Activator-binding Sequence in the Escherichia coli kdpABC Promoter

Microorganisms that accumulated the eicosapentaenoic acid (EPA)-enriched triacylglycerol (TG), were screened for using yeast-malt medium containing 1% free EPA. The best strain was identified as Mucor hiemalis HA-30. The optimum culture conditions for the accumulation of EPA-enriched TG were : 3% soluble starch, 0.5% polypeptone, 0.3% yeast extract, 0.5% free EPA, and pH 6.0 at 25°C. After the cultivation, 1.77 mg/ml of the TG with EPA purity of 79% was obtained. The EPA content in TG increased in conjunction with the EPA content of the supplemented free fatty acids or ethyl esters. Free EPA were more efficiently incorporated than the ethyl esters. Trieicosapentaenoyl glycerol (EPA, EPA, EPA) accounted for 73% of total TGs.     

Urea-hydrolyzing activity of a T-strain mycoplasma: Ureaplasma urealyticum.

The urea-hydrolyzing activity of a T-strain mycoplasma was studied in experiments using whole cells and cell-free enzyme preparations by measuring the release of 14CO2 from [14C]urea. Under the conditions used, the urea concentration optimum is approximately 5.6 X 10(-3) M urea. The activity is soluble and not membrane bound. It is stable at -70 C for several weeks but is more labile at higher temperatures. The pH optimum is between 5.0 and 6.0. The effect of several inhibitors on the activity was tested and revealed similarities, as well as differences, between T-strain mycoplasma urease activity and the urease activity of other organisms and plants.     

Influence of nutritional conditions on exopolysaccharide production by submerged cultivation of the medicinal fungus <Emphasis Type="Italic">Shiraia bambusicola</Emphasis>

Maltose and yeast extract were the most favourable carbon and nitrogen sources for exopolysaccharide production by submerged culture of Shiraia bambusicola WZ-003, and initial maltose and yeast extract concentrations were at 30 and 3 g l⁻¹, respectively. Plant oils could increase the mycelial growth and exopolysaccharide production in tested concentration. K⁺ and Mg²⁺ could enhance the mycelial growth and exopolysaccharide biosynthesis. The optimal cultivation temperature and initial pH were found to be 26°C and 6.0, respectively. Exopolysaccharide concentration reached 0.53 g l⁻¹ in 15-l fermenter under optimal nutritional conditions.     

高生物量富硒酵母的选育及培养条件初步优化

通过筛选、单倍体分离、诱变和原生质体融合,从融合子中选育了一株高生物量富硒酵母菌株（编号为ZFF-28）,其细胞硒总含量分别是原始亲株ZY-67和ZY-198的2.8倍和2.0倍。通过单因素实验和正交试验设计,确定了优化培养条件：6%糖浓度的蔗糖糖蜜,添加0.5% (NH4)2SO4、0.1% H3PO4、60μg/mL Se,pH60～6.5,装液量50mL/250mL三角瓶,接种量10%,培养时间25h。在优化培养条件下,菌株ZFF_28的生物量可达8.2g/L,细胞中硒的含量达2050μg/g,硒总含量达到了16810μg/L,是培养条件优化前的1.3倍。细胞硒含量的91%为有机硒。     

Occurrence of urease in T strains of Mycoplasma

A previously unknown metabolite necessary for growth of T strains of Mycoplasma in artificial culture media has been identified as urea. The source of this metabolite was the mammalian plasma or serum enrichment of the culture medium. Normal horse serum was the most satisfactory native protein enrichment for cultivation of T strains of mycoplasma, and it is believed that its superior performance in agar and fluid culture media is associated with its relatively high urea content (approximately 40 mg/100 ml). T-strain urease activity was maximal at pH 6.0 +/- 0.5. This is also the optimal pH for growth of T strains. Substrate concentrations greater than 1.0% urea were inhibitory to growth and urease activity of T-strain organisms, and optimal urea concentrations in fluid media appeared to lie within the range of 0.008 to 0.01 m. This range of urea concentration permitted maximal growth of T-strain organisms without rapid loss of viability due to excessive ammonia accumulation and rise in pH to lethal levels. T strains of Mycoplasma were cultivated in a serum-free fluid medium containing urea as the only added metabolite and nitrogen source. T strains are the only known human mycoplasmas which exhibit urease activity, and this biochemical marker can be employed as an aid in the detection and identification of T strains of Mycoplasma (urease color test) and in distinguishing T strains from other members of the human Mycoplasma group.     

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.     

Propionic acid fermentation of lactose by Propionibacterium acidipropionici: effects of pH

Batch propionic acid fermentation of lactose by Propionibacterium acidipropionici were studied at various pH values ranging from 4.5 to 7.12. The optimum pH range for cell growth was between 6.0 and 7.1, where the specific growth rate was approximately 0.23 h(-1). The specific growth rate decreased with the pH in the acids have been identified as the two major fermentation products from lactose. The production of propionic acid was both growth and nongrowth associated, while acetic acid formation was closely associated with cell growth. The propionic acid yield increased with decreasing pH; It changed from approximately 33% (w/w) at pH 6.1-7.1 to approximately 63% at pH 4.5-5.0. In contrast, the acetic acid yield was not significantly affected by the pH; it remained within the range of 9%-12% at all pH values. Significant amounts of succinic and pyruvic acids were also formed during propionic acid fermentation of lactose. However, pyruvic acid was reconsumed and disappeared toward the end of the fermentation. The succinic acid yield generally decreased with the pH, from a high value of 17% at pH 7.0 to a low 8% at pH 5.0 Effects of growth nutrients present in yeast ex-tract on the fermentation were also studied. In general, the same trend of pH effects was found for fermentations with media containing 5 to 10 g/L yeast extract. However, More growth nutrients would be required for fermentations to be carried out efficienytly at acidic pH levels.     

Growth of Chlorella pyrenoidosa in wastewater from cassava ethanol fermentation

In a cycle tubular photobioreactor, Chlorella pyrenoidosa was cultured in undiluted wastewater from ethanol fermentation using cassava powder as raw material. The results showed that the optimum cultivation conditions were initial pH of 6.0, temperature at 27°C, continuous illumination at 3,000 lux, and cycle speed of 110 ml min⁻¹. Under these optimum conditions, after the logarithmic phase of batch cultivation with wastewater of pH 6.0, the reactor could be continuously operated with natural pH wastewater (3.8) as feed solution. By a dilution ratio of 0.17 day⁻¹, it could be operated stably for over 30 days in continuous cultivation. pH, removal rate of chemical oxygen demand, and biomass (cell dry weight) concentration ranged from 6.22 to 6.47, 72.21 to 76.32% and 3.55 to 3.73 g l⁻¹, respectively. After treatment, the wastewater could be used again in the process of ethanol fermentation.     

Inulinase production by a marine yeast <Emphasis Type="Italic">Pichia guilliermondii</Emphasis> and inulin hydrolysis by the crude inulinase

Marine yeast strain 1, isolated from the surface of a marine alga, was found to secrete a large amount of inulinase into the medium. This marine yeast was identified as a strain of Pichia guilliermondii according to the results of routine yeast identification and molecular methods. The crude inulinase produced by this marine yeast worked optimally at pH 6.0 and 60°C. The optimal medium for inulinase production was seawater containing 4.0% (w/v) inulin and 0.5% (w/v) yeast extract, while the optimal cultivation conditions for inulinase production were pH 8.0, 28°C and 170 rpm. Under the optimal conditions, over 60 U ml⁻¹ of inulinase activity was produced within 48 h of fermentation in shake flasks. A large amount of monosaccharides and a trace amount of oligosaccharides were detected after the hydrolysis, indicating that the crude inulinase had a high exoinulinase activity.