The influence of the ion content of whey on the pH-activity profile of the β-galactosidase from Aspergillus oryzae

The pH-dependence of the reaction kinetics of lactase (β-galactosidase) from Aspergillus oryzae in different reaction media is presented in terms of a two-parameter model. The lactase from A. oryzae seems to have replaced the A. niger lactase on the market owing to a better activity/price ratio and may be utilised for lactose hydrolysis in acid as well as in neutral milk products. Its pH optimum is around pH 4.5. However, in the neutral pH-range its activity depended strongly on the salt content of the substrate solution. For example, its activity in whey (pH 6.5) fell to only 30% of its expected activity in a pure lactose solution at the same pH. The whey effect was the same for both soluble and immobilised lactase. The two parameter kinetic model, which included a term for competitive product inhibition gave excellent agreement with experimental data, and may thus be useful for the prediction of reactor performance with this enzyme.     

转盘反应器固定米根霉的L－乳酸发酵

研究了米根霉的固定化方法，研制了用吸附法固定米根霉的生物转盘反应器，考察了在该反应器中培养基组成及其它操作条件对Ｌ－乳酸发酵的影响。实验结果表明，应用吸附法固定化的米根霉及生物转盘反应器进行Ｌ－乳酸发酵具有发酵速率快，Ｌ－乳酸得率高及既能用于连续发酵又能用于间歇发酵等优点     

米曲霉在牛乳中最适生长条件的研究

利用米曲霉对牛乳进行发酵,通过单因子及正交试验以菌丝体干重为指标对其在牛乳中的生长进行了研究．结果表明：接种量为4％,装液量为30mL,摇床转速为180r／min时菌丝体干重可达到最大．此外测得最大菌丝体干重时的蛋白质分解率可达35．6％．     

酱油曲菌的选择及酱油发酵条件

研究了日本酱油生产菌AspergillusoryzaeJP DQ 1,AspergillusoryzaeJP W和我国酱油生产菌AspergillusoryzaeAS3.951的酶系。结果表明:3种菌在浓酱油曲和白酱油曲培养基上均可产生α 淀粉酶、糖化酶、纤维素外切酶、果胶酶、酸性蛋白酶和中性蛋白酶;JP W是较好的白酱油生产菌,JP DQ 1是较好的浓酱油生产菌。还对酱油酵母的生理特性进行了部分研究,发现食盐浓度对酱油酵母生长影响较大,酱油发酵过程的盐浓度不宜超过3mol／L,低于2mol／L更佳。酱油酵母的较适生长pH为4.5～5.5。     

Construction of the mutant strain in Aspergillus oryzae 3.042 for abundant proteinase production by the N+ ion implantation mutagenesis

Because of secreting large amounts of enzymes, Aspergillus oryzae was widely used in the fermentation of soy sauce in many Asian countries. Here, N⁺ ion implantation mutagenesis was applied to improve the ability of A. oryzae to secrete acid protease. Several mutants were screened using three kinds of plates (Casein medium, Czapek’s medium and carboxymethyl cellulose medium agar plates). Compared with the other mutants, the mutant A100‐8 could secrete the most protease. Acid protease activity of A100‐8 was enhanced about 44.1% at 36 h by koji fermentation test. In addition, A100‐8 was stable by periodically subculturing and maintaining on the agar slant. The mRNA expression levels of two kinds of acid protease (serine carboxypeptidase and aspartyl protease) were measured by RT‐PCR at different periods. Serine carboxypeptidase and some kinds of aspartyl protease of A100‐8 were significantly (P < 0.01) expressed higher than the control at all times.     

微波-紫外灭活原生质体融合选育米曲霉菌株的研究

实验对生长速度较快但产酶能力较低的米曲霉CICC2339的原生质体采用700W微波灭活12s,对产酶能力较高但生长速度较慢的米曲霉AS3.951的原生质体采用15W紫外灭活5min,然后对灭活双亲用PEG作融合剂进行原生质体融合,融合率达到了7.6%。通过测定Hc值以及蛋白酶活力大小,最终筛选出编号为CAW202、CAW205和CAW210的三株融合株,其生长速度快且蛋白酶活力还高于产酶能力较高的亲本菌株CICC2339;三株融合株的蛋白酶活力分别为10450U/g、9730U/g、10780U/g,其中融合株CAW202和CAW210的蛋白酶活力比亲本菌株CICC2339有了显著的增加,分别提高了7.8%和11.25%。     

反相HPLC双检测器法同时测定米根霉乳酸发酵液中的有机酸与葡萄糖

提出了用高效液相色谱法同时测定米根霉乳酸发酵液中的有机酸和葡萄糖。用Ｗａｋｏｓｉ－Ⅱ５Ｃ１８ＲＳ（４．６ｍｍ＊１５０ｍｍ,５μｍ）色谱柱,以０．０１ｍｏｌ／Ｌ磷酸水溶液（ＰＨ２．５）为流动相,流速１ｍｌ／ｍｉｎ,利用有机酸及葡萄糖对紫外光吸收强弱的差异,采用双检测器系统,以示差折光检测器检测葡萄糖,以可变波长检测器检测有机酸,一次进样可同时定性及定量分析待测样中的有机酸及葡萄糖,每个样品的分析过程     

曲霉发酵甘油生产1,3-丙二醇的研究

从实验室常规霉菌米曲霉和黑曲霉出发,通过唯一碳源法筛选出2株可发酵甘油生产1,3-丙二醇的菌株,并建立了气相色谱检测甘油和1,3-丙二醇的方法,用于测定实际发酵液中1,3-丙二醇的含量。目前有关微生物法生产1,3-丙二醇的研究主要集中在几种条件致病菌上,采用霉菌既考虑了安全问题,又丰富了1,3-丙二醇发酵法生产的可用菌株,为进一步的产业化打下基础。     

沪酿3．042米曲霉的纯化复壮

本文报告了酱油生产的主要菌种沪酿3．042米曲霉的纯化复 的方法,并对复的新茵株,退化菌株,原始菌株的酶活力,孢子数,生长速度等进行了比较,结果表明,经纯化复壮筛选出的菌株其上述三项指标接近甚至超过原始菌株。     

米曲霉菌种选育的研究进展

介绍了诱变育种、原生质体融合及基因工程技术在米曲霉茵种选育中的应用及研究进展。