高产葡萄糖耐量因子酵母的筛选及其发酵特性的研究

通过将供试菌株接种于梯度浓度含铬YEPD平板和液体YPD培养基中进行固体培养及液体发酵试验,利用氨水提取GTF和火焰原子吸收光谱法检测其有机铬含量,从本试验室收藏7株酵母菌种和7株经航天诱变育种的酵母菌种中筛选得到一株葡萄糖耐量因子的高产酵母,有行机铬含量达1287ug/g,总铬含量达1917ug/g.同时研究了菌体发酵过程中,菌体有机铬富集量和其发酵参数的动态关系.     

丝孢酵母高甲硫氨酸突变株的选育及营养调控

以丝孢酵母(Trichosporon Behr)ST851为原始菌株,经紫外线诱变,在含乙硫氨酸的双层平板上筛选到多株抗乙硫氨酸突变株。其中ST851-10株抗乙硫氨酸浓度达到350μg/ml,其菌体蛋白质含量由40.5％提高到44.3％,菌体甲硫氨酸含量由20.45mg/g-DCW增加到29.32mg/g-DCW。在以苹果渣为碳源、尿素为氮源、硫酸镁作硫源的最适培养条件下,固态发酵24h后,蛋白质和甲硫氨酸含量较原始菌株分别提高了15.8％和44.9％。培养基中C/N值低有利于甲硫氨酸的合成,C/N值高则适合于菌体生长。在苹果渣固态发酵过程中,适当补加氮源既有利于菌体生长和甲硫氨酸的合成,又可起到调节培养基pH值的作用。     

高生物量富硒酵母的选育及发酵条件的研究

采用硒浓度耐性培养,从8株酿酒酵母中筛选驯化得到一株高生物量富硒酵母菌株NH-7,并对其发酵条件进了行优化。采取流加培养,在菌株稳定期,即18 h开始分批添加亚硒酸钠至总硒浓度为30μg/mL,控制乙醇浓度为0.4%和0.7%,分别得到20.14 g的高生物量(每升培养液中获得的酵母菌体干重)和82.52%的硒转化率。在60μg/mL总硒浓度的流加培养中,得到高达2 411μg/g的有机硒含量,每升发酵液菌体干重为18.83 g。     

皮状丝孢酵母B3利用木薯淀粉发酵生产微生物油脂

对皮状丝孢酵母B3以木薯淀粉水解液为碳源发酵生产微生物油脂培养条件进行了优化,并在2 L发酵罐中对菌体生长和油脂积累进行了考察。摇瓶实验表明,木薯淀粉水解液的浓度高于90 g/L时不利于菌体的生长和油脂积累,皮状丝孢酵母B3发酵生产微生物油脂的最适氮源及其浓度、最适C/N比和pH分别为酵母提取物3.0 g/L、116、6.0,在此条件下培养144 h菌体生物量、油脂产量和油脂含量分别达到15.2 g/L、6.22 g/L和40.9％;在2 L发酵罐中分批发酵44 h后菌体生物量、油脂产量和油脂含量分别达28.7 g/L、12.27 g/L和42.8％。以皮状丝孢酵母B3所产油脂制备生物柴油,其主要组成包括棕榈酸甲酯、硬脂酸甲酯、油酸甲酯、亚油酸甲酯等,且理化特性符合相关国家标准,可作为一种有潜力的化石燃料替代品。     

红酵母类胡萝卜素形成的生理学研究

从数株红酵母中选出 1株产类胡萝卜素能力较强的红酵母RY 98(生物量、类胡萝卜素含量和产量分别为19.9g/L ,334 .8μg/ g和 6 .7mg/L) ;研究了该菌株产类胡萝卜素的最适营养与环境条件 ,获得了最佳的发酵生理学条件 :葡萄糖 40 g/L ,(NH4 ) 2 SO4 10 g/L ,酵母膏 3g/L ,蕃茄汁 2mL/L ,花生油 0 .5mL/L ,接种量 30mL/L ,初始pH 6 .0和通气量 (培养基装量 ) 4 0mL/ 2 5 0mL。在此初步优化的培养条件下 ,红酵母RY 98经 72h摇瓶发酵其生物量、类胡萝卜素含量和产量分别可达 2 6 .8g/L ,386 .9μg/ g和 10 .4mg/L ,依次比初筛中提高了 34 .7% ,15 .6 %和 5 5 .2 %。     

海洋中海藻糖产生菌的筛选及发酵条件优化

从180余份海水、海泥样品中筛选得到60株产海藻糖较高的菌株,编号为2-14的菌株海藻糖产量最高,为127.9mg/g cell。对2-14菌株进行形态特征、培养特征及生理生化试验,鉴定该菌株为红酵母属(Rhodotorula sp.)。研究摇瓶发酵条件对红酵母海藻糖产量的影响,结果为:初始pH5.5,发酵温度28℃,装液量75mL(250mL三角瓶中)。采用优化后发酵条件红酵母海藻糖产量为193.3mg/g cell,优化前对照值为132.1mg/g cell,优化后的结果是优化前的1.46倍。在5L发酵罐中培养得到最佳发酵时间为54h,发酵罐培养发酵液中海藻糖含量最高达2.5g/L,为摇瓶培养的1.6倍。     

红酵母类胡萝卜素高产菌株的筛选及其发酵生理学条件研究

从数株红酵母中选出了1株产类胡萝卜素能力较强的红酵母RY－98（生物量,类胡萝卜素含量和产量分别为19．9g/L,334.8ug/g和6．7mg/L);研究了该菌株产类胡萝卜素的最适营养与环境条件,获得了最佳的发酵生理学条件;葡萄糖40g/L,(NH4)2SO4 10g/L,酵母膏3g/L,蕃茄汁2mL/L,花生油0.5mL/L,接种量30mLL初始pH6.0和通气量（培养基装置040ml/250mL:,在此初步优化的培养条件下,红酵母RY－98经72小时摇瓶发酵其生物量,类胡萝卜素含量和产量分别可达26．8g/L,386.9ug/g和10．4mg/L,依次比初筛中提高了34．7％,15．6％,和55．2％。     

5种商业酵母对无花果酒质量的影响

为筛选出适合无花果酒发酵的菌株,选用五株商业酵母通过对发酵性能、理化指标、总酚、甲醇、感官评定进行比较分析。实验表明,菌株KD主发酵CO_2失重量为14.85 g,酒精度可达11.52%(V/V),透光率(96.7 T%)显著高于其它菌株(p0.05),总酸为3.55 g/L,酒中总酚含量为0.37 mg/L,甲醇含量为297.19 mg/L显著低于其它菌株(p0.05)。菌株KD发酵的无花果酒感官评分高于其它菌株发酵的酒,其风格独特,典型优雅。本试验通过从商业酵母中筛选出适合无花果酒发酵的优良酵母,可为无花果酒的生产提供理论依据。     

固态发酵下酵母自溶的工艺优化

固态下酵母自溶可以有效促进菌体内多种活性物质的释放,进而提高酵母类产品的品质。通过优化自溶温度、自溶时间及自溶促进剂锌离子浓度以获得固态发酵下酵母自溶的最佳工艺,对固态发酵物料中游离氨基酸、可溶性蛋白、α-氨基氮含量和A260/A280等指标的分析来确定固态酵母自溶工艺条件,在此基础上以自溶温度40 ℃、50 ℃、55 ℃;作用时间12、18、24 h;锌离子添加浓度2、4、8 mg/kg设置L9(33)正交试验,进一步优化固态酵母自溶的工艺参数。结果表明酵母自溶的最佳工艺条件为：自溶温度55 ℃、作用时间18 h、锌离子浓度2 mg/kg,此时其可溶性蛋白含量可达9.31 mg/g、游离氨基酸14.36 mg/g、α-氨基氮10.16 μg/g、A260/A280为1.73。经工艺优化后,可显著提高酵母自溶产物可溶性蛋白、游离氨基酸和α-氨基氮的含量,从而明显提高了复合菌培养物的品质。     

超嗜热酯酶EST2在不同宿主中的异源高效表达研究

来源于超嗜热古菌Alicyclobacillus acidocaldarius的酯酶EST2是目前报道的活性最高的超嗜热酯酶,具有极大的工业应用价值。为促进EST2的生产应用,将其分别在大肠杆菌及毕赤酵母中进行异源表达,并就不同宿主对表达情况和重组酶酶学性质的影响进行了分析。在大肠杆菌和毕赤酵母中重组表达的EST2酶学性质基本一致:最适温度分别为75℃和77.5℃,最适pH均为8.0,比活力分别为4656.6 U/mg和4078.3 U/mg,70℃水浴保温4.5 h,残余活力均在70%以上。在摇瓶发酵的基础上,于5 L发酵罐中进行了重组大肠杆菌及毕赤酵母的高密度发酵。毕赤酵母高密度发酵120 h菌体干重达68 g/L,最大表达酶活力为959.6 U/ml。大肠杆菌高密度发酵25 h菌体干重达60.8 g/L,最大酶活力14825.6 U/ml,表达量是毕赤酵母的15.4倍,单位时间产量是酵母的74.2倍。结果表明大肠杆菌发酵周期短、表达量高,更适合进行嗜热酯酶EST2的高效生产,这为促进嗜热酯酶在工业生物技术产业的应用奠定了基础。     

Bioremediation of chromium by the yeast Pichia guilliermondii: toxicity and accumulation of Cr (III) and Cr (VI) and the influence of riboflavin on Cr tolerance

A comparative study has been made on the sensitivity of the yeast Pichia guilliermondii to Cr (III) and Cr (VI) as well as on the Cr uptake potential at growth-inhibitory concentrations of chromium. The strains used in the study were either isolated from natural sources or obtained from a laboratory strain collection. The results show that most of the natural strains were more tolerant to chromium and were able to grow in the presence of 5 mM Cr (III) or 0.5 mM Cr (VI), that is at concentrations which substantially inhibited the growth of laboratory strains. The cellular Cr content after treatment was similar for both strain types and ranged from 1.2-4.0 mg/g d.w. and 0.4-0.9 mg/g d.w., for Cr (III) and Cr (VI) forms, respectively, however, in one case of a natural strain it reached the value of 10 mg Cr (III)/g dry mass. Natural-source strains were grouped into four groups based on the yeasts' differential response to Cr (III) and Cr (VI). Hexavalent Cr-resistant mutants of a P. giuilliermondii laboratory strain, which revealed markedly changed capabilities of chromium accumulation, were obtained by means of UV-induced mutagenesis. Cr (VI) treatment triggered oversynthesis of riboflavin and the addition of exogenous riboflavin increased P. guilliermondii resistance to both Cr (III) and Cr (VI). Electrophoretic protein profiles revealed the induction and/or suppression of several proteins in response to toxic Cr (VI) levels.     

Selection of a high-biomass, chromium-rich yeast strain and optimization of cultivation conditions

Saccharomyces cerevisiae LZ-53 was selected from 240 primary yeast strains from different genera and species, whose chromium (Cr) resistance and biomass were higher than others were. The highest biomass and Cr content of the strain was obtained in 30 h at 28°C and 200 rpm, when 20 ml of the culture in 250-ml shake flasks was grown in wort containing 1200 μg/ml Cr. The initial pH was adjusted to 6.0. The optimal inoculum volume was 10% (v/v). The Cr content of the cells was determined by neutron activation analysis. Under the optimized cultivation conditions, the Cr content reached 3248 μg/g. Journal of Industrial Microbiology & Biotechnology (2001) 27, 195–198. Received 28 January 2001/ Accepted in revised form 11 June 2001     

糖蜜发酵培养富铬酵母

筛选对铬元素吸收较好的产朊园酵母(Torulopsisutilis)为实验菌株,根据铬的耐受量实验,确定糖蜜培养基铬的添加量,研究富铬酵母培养最佳工艺条件,探讨富铬酵母的应用。发酵产品富铬酵母铬的含量7388mgkg,蛋白质含量4874%(ww),得率30%(wv)。     

Effects of Selenium- and Chromium-Enriched Diets on Growth Performance,Lipid Profile,and Mineral Concentration in Different Tissues of Growing Rabbits

The aim of this study was to investigate the effect of dietary supplementation with different sources of selenium and/or organic chromium on the growth performance, digestibility, lipid profile, and mineral content of hair, liver, and fore and hind limb of growing rabbits. A total of 150 weanling New Zealand White (NZW) male rabbits were randomly allotted to six dietary treatment groups: (1) basal diet (control group), (2) basal diet + 0.6 mg sodium selenite/kg diet, (3) basal diet + 0.6 mg selenium yeast/kg diet, (4) basal diet + 0.3 mg sodium selenite/kg diet + 0.3 mg selenium yeast/kg diet, (5) basal diet + 0.6 mg chromium yeast/kg diet + 0.6 mg selenium yeast/kg diet, (6) basal diet + 0.6 mg chromium yeast/kg diet. Only the combination between inorganic and organic selenium led to significant improvement in body weight, body weight gain, and feed conversion ratio. Carcass traits were not different in all groups. Selenium (Se) and chromium (Cr) were deposited in the tissues of rabbits fed diets supplemented with Se and Cr, respectively. Blood serum in both of selenium- and chromium-supplemented groups showed declined total cholesterol, triglycerides, and low-density lipoprotein (LDL). Group supplemented with organic chromium showed higher high-density lipoprotein (HDL) than the other groups. It could be concluded that using a mixture of inorganic and organic Se has a positive effect on the growth performance of growing rabbits. Both Se and Cr have hypocholesterolemic effect. Both of Se and Cr can be deposited in the meat and other tissues of rabbits and that improves meat quality which positively reflects on human acceptance. The combination between inorganic (0.3 mg sodium selenite/kg diet) and organic selenium (0.6 mg selenium yeast/kg diet) improved growth performance traits of growing rabbits.

     

一株高产Monacolin K紫红曲霉菌株筛选、鉴定及发酵条件优化

为从天然发酵红曲米中分离的30株红曲霉菌株中筛选高产MonacolinK的菌株,并对其产MonacolinK的发酵条件进行优化。实验采用高效液相色谱法(HPLC)筛选到9株具有产MonacolinK能力的红曲霉菌株,其中以编号ZX26的菌株产MonacolinK能力最高,发酵液中Monacolin K产量达到107.6mg/L,并且产MonacolinK能力具有良好的稳定性。微生物形态学结合ITS基因同源性分析结果表明,编号ZX26菌株为紫红曲霉。进一步采用单因素试验和正交试验法优化紫红曲霉ZX26产MonacolinK的发酵条件,结果表明在培养基组分为葡萄糖70g/L,牛肉膏15g/L,NaNO32g/L,MgSO4·7H2O0.5g/L,KH2PO41.5g/L时,其最优发酵条件为:发酵初始pH4.0,接种量为7%,培养温度30℃,发酵10天,在此条件下,紫红曲霉ZX26发酵液中MonacolinK产量达到271.36mg/L,相对于培养条件优化前MonacolinK产量提高152.19%,经验证此培养条件下MonacolinK产量最佳。     

几株啤酒酵母的筛选及发酵性能比较*

啤酒酵母是啤酒酿造的灵魂,可以直接影响啤酒品质。在啤酒酿造过程中,由于啤酒酵母被多次传代和保藏,造成优良菌种发酵性能衰退等问题,导致发酵不彻底,影响最后啤酒的风味质量。为此以8株Lager型啤酒酵母为出发菌株,通过平板分离纯化获得80株分离菌株,再经过三角瓶发酵初筛和复筛、发酵罐中试发酵实验最终获得了8株发酵性能优良的啤酒酵母。其中,6株酵母可应用于酿造双乙酰含量低于0.1 mg/L的啤酒;3株酵母发酵度高于70%,适合酿造干啤酒;1株酵母发酵度低于50%,适合酿造低醇啤酒。在风味方面:1株酵母酿造的啤酒醇酯比为3.3,啤酒酯香味较突出;另1株酵母酿造的啤酒醇酯比为4.5,啤酒高级醇含量较高。8株经过选育的啤酒酵母发酵特征明显,便于精酿啤酒厂实际应用。     

Chromium accumulation by living yeast at various environmental conditions

Yeast tolerance to Cr (III) and Cr (VI) as well as chromium accumulation potential were shown to depend on treatment time, metal concentration, biomass density and the phase of growth. Kinetic studies as exemplified by Pichia guilliermondii ATCC 201911 revealed a biphasic mode of Cr (III) uptake: a rapid sorption phase was followed by a slow process of accumulation, in which the contribution of the cell-bound Cr fraction increased, while the total cellular Cr level remained constant. Cr (VI) uptake was characterized by a time-dependent increase of total Cr and by a constant fractional contribution of the cell-adsorbed chromium, which suggests that the amount of cell-accumulated Cr also tended to increase over time. The resistance to Cr and metal accumulation levels were substantially elevated for a given strain when cultures were treated at high initial biomass densities (1 mg dry weight/ml) of exponentially proliferating cells. Maximum accumulation capabilities ranged between 4.0 and 13 mg Cr (III)/g dry weight and 2-6.7 mg Cr (VI)/g dry weight. The total cell-accumulated Cr contained 29.3% and 52.3% of organically bound chromium for the treatment of P. guilliermondii with Cr (III) and Cr (VI), respectively. Selected yeast strains, under specified physiological conditions, can be applied for bioremediation of environmental Cr contamination, and might be useful too for attempts to obtain chromium-enriched biomass containing biostabilized and nontoxic Cr forms for nutritional applications.     

高生物量富铁酵母菌的选育及其发酵条件的研究

对402株不同种属的酵母菌株进行初筛、复筛,筛选到一株生物量较高的二倍体菌株ZY-46(Saccharomyces cerevisiae)和一株铁富集量较高的二倍体菌株ZY-173(Saccharomyces kluyveri)。然后以它们为出发菌,分别进行单倍体分离、硫酸二乙酯(DES)诱变,并通过原生质体融合,得到一株高生物量富铁酵母融合菌株ZYF-15。在优化的发酵条件下,该融合菌株生物量可达11．2g／L,细胞铁含量达24．5mg／g干细胞,细胞总铁含量分别比原始亲株ZY-46和ZY-173提高了2．6倍和1．9倍。     

Xylose fermentation by genetically modified Saccharomyces cerevisiae 259ST in spent sulfite liquor

Spent sulfite pulping liquor (SSL) is a high-organic content byproduct of acid bisulfite pulp manufacture which is fermented to make industrial ethanol. SSL is typically concentrated to 240 g/l (22% w/w) total solids prior to fermentation, and contains up to 24 g/l xylose and 30 g/l hexose sugars, depending upon the wood species used. The xylose present in SSL is difficult to ferment using natural xylose-fermenting yeast strains due to the presence of inhibitory compounds, such as organic acids. Using sequential batch shake flask experiments, Saccharomyces cerevisiae 259ST, which had been genetically modified to ferment xylose, was compared with the parent strain, 259A, and an SSL adapted strain, T2, for ethanol production during SSL fermentation. With an initial SSL pH of 6, without nutrient addition or SSL pretreatment, the ethanol yield ranged from 0.32 to 0.42 g ethanol/g total sugar for 259ST, compared to 0.15-0.32 g ethanol/g total sugar for non-xylose fermenting strains. For most fermentations, minimal amounts of xylitol (<1 g/l) were produced, and glycerol yields were approximately 0.12 g glycerol/g sugar consumed. By using 259ST for SSL fermentation up to 130% more ethanol can be produced compared to fermentations using non-xylose fermenting yeast.     

Ergosterol production from molasses by genetically modified <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Ergosterol is an economically important metabolite produced by fungi. Recombinant Saccharomyces cerevisiae YEH56(pHXA42) with increased capacity of ergosterol formation was constructed by combined overexpression of sterol C-24(28) reductase and sterol acyltransferase in the yeast strain YEH56. The production of ergosterol by this recombinant strain using cane molasses (CM) as an inexpensive carbon source was investigated. An ergosterol content of 52.6 mg/g was obtained with 6.1 g/l of biomass from CM medium containing 60 g/l of total sugar in 30 h in shake flask. The ergosterol yield was enhanced through the increasing cell biomass by supplementation of urea to a concentration of 6 g/l in molasses medium. Fermentation was performed in 5-l bioreactor using the optimized molasses medium. In batch fermentation, the effect of agitation velocity on ergosterol production was examined. The highest ergosterol yield was obtained at 400 rpm that increased 60.4 mg/l in comparison with the shake flask culture. In fed-batch fermentation, yeast cells were cultivated, firstly, in the starting medium containing molasses with 20 g/l of total sugar, 1.68 g/l of phosphate acid, and 6 g/l of urea (pH 5.4) for 5 h, then molasses containing 350 g/l of total sugar was fed exponentially into the bioreactor to keep the ethanol level in the broth below 0.5%. After 40 h of cultivation, the ergosterol yield reached 1,707 mg/l, which was 3.1-fold of that in the batch fermentation.