假丝酵母一新种——北京假丝酵母

本文研究了一株从水果表皮分离到的假丝酵母,它与至今已发表的所有已知假丝酵母均不相同,定名为北京假丝酵母(Candida beijingensis)。     

假丝酵母同源性的研究

用分光光度法测定了4株郎比可假丝酵母(Candida lambica)间的DNA-DNA同源性,结果:2.1182与LP012的同源性为90.4%,表明它们是同种的;2.1182与DX22为77.5%,DX22与LP012为76.8%,表明它们虽是同种,但产生了一些分化:LP006与LP012为63.2%,表明它们之间产生了较大的分化,接近种的范围,仍可认为是同种的。     

假丝酵母产生物表面活性剂的研究

从扬子石化的废水淤泥中筛选到1株假丝酵母(Candida),其发酵上清液有较强的表面活性,可将水的表面张力从72.3mN/m降到32.5mN/m。发酵上清液经酸化、丙酮沉淀后得到浅黄色固体,经TLC、IR、GC-MS分析表明:此种物质为脂肽类物质,疏水基部分为十六碳酸和9-十八烯酸,亲水基部分含有多种氨基酸。其临界胶束质量浓度为150mg/L,可耐受120℃高温和饱和浓度盐离子(质量分数为36%的Na+),pH适应范围广(pH2～12),是一种极具应用前景的生物表面活性剂。     

假丝酵母尿酸酶形成条件

选出了一株产尿酸酶的产朊候丝酵母(Candida utilis)AS2．117。此菌株尿酸酶形成条件的研究表明：尿酸、黄嘌呤和鸟嘌呤对酶形成起诱导作用;玉米浆对菌株生长和酶形成起十分重要的作用;蔗糖、葡萄塘、D-甘露糖和果糖是酶形成的适合碳源;生物素对酶产生有促进作用;在含有玉米浆培养基中加入无机氮源对产酶无作用,添加有机氮略增加产酶量。尿酸酶形成最适培养基组成为(％)：蔗糖;,玉米浆3,尿酸0．1,蛋白胨0．1,生物素0．05,KCI0．1,NaCl 0.1。最适pH为6．2。在250ml三角瓶中装30ml培养基为最适。在200r／min的旋转摇床上25℃振荡培养21h,在此条件下最终酶活力可达0．6u／ml。     

表型相似的热带假丝酵母和麦芽糖假丝酵母在脉冲电泳核型上的差异

热带假丝酵母Ｃａｎｄｉｄａ ｔｒｏｐｉｃａｌｉｓ （Ｃａｓｔｅｌｌａｎｉ ）Ｂｅｒｋｈｏｕｔ和麦芽糖假丝酵母Ｃ． ｍａｌｔｏｓａＫｏｍａｇａｔａ, Ｎａｋａｓｅ ＆ Ｋａｔｓｕｙａ是两种可利用烃类作为碳和能量来源的酵母菌,前者还是一种条件致病菌,可引起系统感染。这两种假丝酵母菌在形态和生理生化性状上非常相似,用常规分类方法不易准确地鉴别。本研究对Ｃ． Ｔｒｏｐｉｃａｌｉｓ和Ｃ ｍａｌｔｏｓａ的模式菌株以及中国普通微生物菌种保藏中心（ＣＧＭＣＣ）保藏的归于这两个种名下的其它菌株进行了脉冲电泳核型比较分析。发现这两个表型相似的种具有明显不同的染色体ＤＮＡ分子带型,而同一种内的不同菌株却具有相同或相似的分子核型。Ｃ．Ｔｒｏｐｉｃａｌｉｓ的特异染色体ＤＮＡ分子带谱为２条８．５—１．２ Ｍｂ的带, ４条２．３－３．４ Ｍｂ的带。 Ｃ ｍａｌｔｏｓａ的特异带谱为： ３～４条分子量在１．１－１．３Ｍｂ范围内的带, １条约为２．２Ｍｂ的带以及２－３条大小为３．２－３．５Ｍｂ的带。 Ｃ ｔｒｏｐｉｃａｌｉｓ与Ｃ ｍａｌｔｏｓａ在染色体ＤＮＡ分子带型上的差异与二者在可溶性淀粉的同化能力和４０℃下的生长能力上的差异具有明显的相关性…     

假丝酵母99-125脂肪酶的发酵工艺研究

对假丝酵母99-125脂肪酶的发酵工艺条件进行了一系列研究。选择了合适的培养基成分并进行优化 ,获得了最优的摇瓶培养基配方 (% ,W/V) :豆油 4.0 ,全脂豆粉 4.0 ,K₂HPO₄0.1,KH₂PO₄ 0.1。产酶水平能达到 5000IU/mL。在 30L发酵罐上进行初步放大实验 ,其产酶水平能达到 8100IU/mL。在1m³发酵罐上进行中试放大 ,产酶水平可达到 8000IU/mL。     

假丝酵母YQ5产S-腺苷甲硫氨酸的发酵培养基优化

利用单因子实验和正交实验对假丝酵母(Candida sp.)突变菌株YQ5摇瓶发酵产生S-腺苷甲硫氨酸的培养基成分进行了优化。单因子实验结果表明, 发酵最适pH值为6.0, 最佳碳源为 8%蔗糖, 最佳氮源为1.5%胰蛋白胨, 酵母粉最适浓度为2%, MgSO4·7H2O、CaCl2、FeSO4·7H2O、CoCl2、CuSO4·5H2O、H3BO3等作为无机离子对胞内S-腺苷甲硫氨酸的积累均有促进作用。利 用正交实验获得了最终的发酵培养基配方。在最适条件下发酵48 h, S-腺苷甲硫氨酸含量可达1740.0 mg/L。     

Four novel <Emphasis Type="Italic">Candida</Emphasis> species in the <Emphasis Type="Italic">Candida albicans</Emphasis>/<Emphasis Type="Italic">Lodderomyces elongisporus</Emphasis> clade isolated from the gut of flower beetles

Flower-visiting beetles belonging to three species of Cetoniidae were collected on three mountains near Beijing, China, and yeasts were isolated from the gut of the insects collected. Based on the 26S rDNA D1/D2 domain and internal transcribed spacer (ITS) region sequence analysis and phenotypic characterization, four novel anamorphic yeast species located in the Candida albicans/Lodderomyces elongisporus clade were identified from 18 of the strains isolated. The new species and type strains are designated as Candida blackwellae AS 2.3639^T (=CBS 10843^T), Candida jiufengensis AS 2.3688^T (=CBS 10846^T), Candida oxycetoniae AS 2.3656^T (=CBS 10844^T), and Candida pseudojiufengensis AS 2.3693^T (=CBS 10847^T). C. blackwellae sp. nov. was basal to the branch formed by C. albicans and C. dubliniensis with moderately strong bootstrap support. The closest relative of C. oxycetoniae was L. elongisporus. C. jiufengensis sp. nov. and C. pseudojiufengensis sp. nov. were closely related with each other and formed a branch in a subclade represented by C. parapsilosis and L. elongisporus.     

3-羟基丙酸高产菌株的筛选及诱变选育

【目的】3-羟基丙酸是一种重要的化学平台化合物,期望得到一株能够高产3-羟基丙酸的菌株。【方法】从土壤及粪便筛选并对得到的菌株进行鉴定和复合诱变。【结果】得到了一株能够利用丙酸发酵生产3-羟基丙酸的酵母Y-11,经生理生化鉴定及18S rDNA序列分析确定其为Candida sp.(假丝酵母)。以Y-11为出发菌株,经紫外-亚硝基胍-60Coγ复合诱变得到了突变性状稳定且可遗传的高产菌株5-13B,其3-羟基丙酸的产量为11.78 g/L,是出发菌株的2.46倍。【结论】对出发菌株和突变株的发酵特性进行了比较,结果表明突变株的3-羟基丙酸产量、对底物丙酸的转化率、产物3-羟基丙酸的积累性能及丙酸的耐受性均优于出发菌株。     

假丝酵母99-125脂肪酶喷雾干燥工艺及催化性质的研究

利用响应面法对假丝酵母脂肪酶喷雾干燥工艺条件进行优化,考察进口温度、雾化速度、保护剂含量对脂肪酶活力收率的影响。确定了最佳喷雾条件:保护剂为10～15 g/L的阿拉伯胶,进口温度115～120℃,雾化速度0.4 L/h,可得到收率最高为60.5%的脂肪酶酶粉。制得的固定化酶用于手性拆分(R,S)-1-苯乙醇,光学产率最高可达到53.6%;用于催化合成生物柴油,转化率最高可达到90.2%。在4、30℃下密封保存,半衰期可分别达到15个月、3个月。     

Candida alocasiicola sp. nov., Candida hainanensis sp. nov., Candida heveicola sp. nov. and Candida musiphila sp. nov., novel anamorphic, ascomycetous yeast species isolated from plants

In a taxonomic study on the ascomycetous yeasts isolated from plant materials collected in tropical forests in Yunnan and Hainan Provinces, southern China, four strains isolated from tree sap (YJ2E(T)) and flowers (YF9E(T), YWZH3C(T) and YYF2A(T)) were revealed to represent four undescribed yeast species. Molecular phylogenetic analysis based on the large subunit (26S) rRNA gene D1/D2 domain sequences showed that strain YJ2E(T) was located in a clade together with Candida haemulonii and C. pseudohaemulonii. Strain YF9E(T) was most closely related to C. azyma and strain YWZH3C(T) to C. sorbophila and C. spandovensis. Strain YYF2A(T) was clustered in a clade containing small-spored Metschnikowia species and related anamorphic Candida species. The new strains differed from their closely related described species by more than 10% mismatches in the D1/D2 domain. No sexual states were observed for the four strains on various sporulation media. The new species are therefore assigned to the genus Candida and described as Candida alocasiicola sp. nov. (type strain, YF9E(T) = AS 2.3484(T) = CBS 10702(T)), Candida hainanensis sp. nov. (type strain, YYF2A(T) = AS 2.3478(T) = CBS 10696(T)), Candida heveicola sp. nov. (type strain, YJ2E(T) = AS 2.3483(T) = CBS 10701(T)) and Candida musiphila sp. nov. (type strain, YWZH3C(T) = AS 2.3479(T) = CBS 10697(T)).     

假丝酵母菌GXU08产脂肪酶发酵条件的优化

以假丝酵母菌GXU08产脂肪酶催化合成麝香类香料—环十五内酯目前已备受关注,在一定条件下,环十五内酯的转化率与脂肪酶的水解酶活有直接关系,酶活越高其催化合成环十五内酯的能力越强。通过单因素试验和正交试验,对假丝酵母菌GXU08产脂肪酶的发酵条件进行优化。结果表明:最佳发酵培养基配方为蔗糖0.5%,淀粉0.5%,蛋白胨1.5%,K_2HPO_40.05%,MgSO_40.15%,(NH_4)_2SO_41%,茶油1.5%,菜籽油1.5%,pH=8,此培养基在28℃,180 r/min的条件下发酵培养48h,脂肪酶水解活力达到27.53 U/mL,是初始发酵培养基条件下所得脂肪酶酶活的3.74倍;其环十五内酯的转化率为16.6%,是优化前的4倍。     

Esterification of streptol — a cyclitol derivative — by Candida rugosa lipase: influence of the acyl donor on regioselectivity

The influence of the nature of acyl donors on the regioselectivity of Candida rugosa lipase for the esterification of streptol — a cyclitol derivative — was investigated. Excellent regioselectivity for the formation of 3,7-disubstituted derivatives was observed for vinyl butyrate (100% 3,7-derivative, 68% yield) and vinyl propionate (100% 3,7-derivative, 46% yield) as acyl donors. In contrast, for vinyl methacrylate as acyl donor, a mixture of 71% 3,7-derivative and 29% 1,7-derivative was obtained. Varying the chain length, a certain dependency of regioselectivity on the acyl donor was observed, however, no logical correlation satisfying all cases was found. Mono-substituted streptol derivatives were obtained by employing Novozym 243.     

Candida spp. redox machineries: An ample biocatalytic platform for practical applications and academic insights

The use of oxidoreductases as biocatalysts for the production of a wide number of chiral building blocks is presently a mature (bio-)technology. In this context some industrial applications are currently performed by means of those enzymatic approaches, and new examples are expected to be realized. Moreover, oxidoreductases provide an interesting academic platform to undertake fundamental research in enzymology, to acquire a better understanding on catalytic mechanisms, and to facilitate the development of new biocatalytic applications. Within this area, a wide number of oxidoreductases from genus Candida spp. have been characterized and used as biocatalysts. These enzymes are rather diverse, and are able to carry out many useful reactions, like highly (enantio)selective keto-reductions, (de)racemizations and stereoinversions, and promiscuous catalytic imine reductions. In addition, some Candida spp. dehydrogenases are very useful for regenerating the cofactors, with the aid of sacrificial substrates. Addressing those features, the present paper aims to give an overview of these enzymes, by focusing on practical applications that these biocatalysts can provide. Furthermore, when possible, academic insights on the enzymatic performances will be discussed as well.     

A novel isolate of Desulfovibrio sp. with enhanced ability to reduce Cr(VI)

Kinetic analysis of the reduction of Cr(VI) by resting cell suspensions of Desulfovibrio vulgaris ATCC 29579 and a new isolate, Desulfovibrio sp. (`Oz7') was studied using lactate as the electron donor at 30 °C. The apparent K <sub>m</sub> (K <sub>m app</sub>) and V <sub>max</sub> with respect to Cr(VI) reduction was compared for both strains. Desulfovibio sp. `Oz7' had a K _{m app} of 90 M (threefold lower than that of D. vulgaris ATCC 29579) and a V _max of 120 nmol h^–1 mg^–1 biomass dry wt (approx. 30% lower than for the reference strain). The potential of the new isolate for bioremediation of Cr(VI) wastewaters is discussed.