十二碳二元酸产生菌热带假丝酵母的诱变

以热带假丝酵母菌(Candida tropicalis)为出发菌株,经紫外线和氯化锂复合诱变或亚硝酸诱变获得突变株。通过摇瓶分批发酵,对菌株诱变前后发酵产长链二元酸量进行了测定。筛选出能够发酵产酸的突变株12株,其中8株表现出正突变,菌株最高产酸量提高了9.16%。     

热带假丝酵母处理红麻亚铵法制浆废液的研究

以红麻亚铵法制浆废液为原料,对热带假丝酵母菌的培养条件进行了研究,结果表明:在原废液浓度9°Be、pH 6.0、发酵温度30℃、接种量10%、发酵时间48h、摇床转速140 r/min、摇瓶装液量50mL/250mL的优化条件下,菌体干重可以达到7.874g.L-1,原废液COD cr下降33%左右,为红麻亚铵法制浆废液资源化利用和降低排放量提供了新的途径。     

醋酸菌培养条件的优化及醋酸分批发酵

目的醋酸菌培养条件的优化与醋酸发酵实验。方法通过正交试验确定最佳培养条件,并在优化条件下进行分批发酵。结果优化培养条件为:葡萄糖10g/L,酵母膏10g/L,乙醇10%(v/v),pH5.5,装量50mL/500mL,静置培养5d。在优化条件下,醋酸产量比用普通产酸培养基提高了36.4%。应用于分批发酵试验产酸较高。结论优化培养条件适合醋酸菌生长与醋酸发酵。     

前体氨基酸对热带假丝酵母产谷胱甘肽的影响

以能利用木糖发酵产谷胱甘肽(GSH)的热带假丝酵母突变株CV26为实验菌株,分别研究了添加L-半胱氨酸、谷氨酸、甘氨酸3种前体氨基酸对CV26产GSH的影响。在单因素实验基础上,对3种前体氨基酸的添加进行了正交实验,结果表明:在GSH发酵的12h添加6mmol/L的甘氨酸和2mmol/L的谷氨酸,24h添加3mmol/L的L-半胱氨酸,GSH的产量和胞内含量都有较大的提高,分别达到149.28mg/L和20.43mg/g,比对照组分别提高了51.5%和57.8%。     

十三碳二元酸发酵与肉毒碱乙酰基转移酶酶活动力学研究

在利用热带假丝酵母发酵生产十三碳二元酸(DCA13)的过程中,建立了用荧光法测定酵母体内肉毒碱乙酰基转移酶(CAT)酶活的方法,方法简单,重现性高,测量精确。研究了热带假丝酵母中CAT酶活动力学与产酸速率的关系,结果表明:代谢前期细胞以生长为主,CAT酶活较高可提供更多的生长动力,而代谢后期细胞进入产酸期,CAT酶活与产酸速率的变化趋势成反比,即产酸速率高时,CAT的酶活较低。     

固定化醋酸杆菌发酵条件的研究

以海藻酸钠为载体,采用包埋法固定化醋酸杆菌,利用固定化醋酸杆菌进行醋酸发酵,寻求其最优工艺参数。在单因素试验的基础上,确定接种量、起始乙醇体积分数和发酵温度为主要影响因素,采用响应面法的Box-Behnken试验设计对发酵条件进行优化。建立产酸量与影响因子的多元二次回归方程,得到固定化醋酸杆菌进行醋酸发酵的最佳条件为:接种量7.88g/100mL,起始乙醇体积分数4.63%,发酵温度32℃,在此条件下,产酸量的理论值为3.56g/100mL。对最佳发酵条件进行实验验证,结果产酸量为3.51g/100mL,与模型预测基本相符。因此,利用响应面分析方法得到的固定化醋酸杆菌发酵条件参数可靠,具有实用参考价值。     

珍珠梅果醋的工艺研究

以云南珍珠梅为原料,沪酿1．41醋酸菌为菌种,经液态深层发酵酿制珍珠梅果醋。分析了温度、接种量、初始酸度、初始酒精度对醋酸发酵的影响,结果表明,珍珠梅果醋酿制的最佳工艺参数为温度32℃,接种量11%(v/v),初始酸度1．8g/100mL(以醋酸计),初始酒精度5．0%(v/v),发酵率达到84．8%。建立了相关方程Y=3．524-3．16X_1~2 1．500X_2~2-0．267X_3 0．567X_4,复相关系数R~2=0．941,醋酸菌在发酵第7d达到对数生长期;酿制出来的珍珠梅果醋经澄清化处理颜色金黄、澄清透亮、醋味浓郁,同时具有珍珠梅的特殊风味。     

Nitrogen fixation associated with grasses and cereals: Recent progress and perspectives for the future

Over the last 20 years many new species of N₂-fixing bacteria have been discovered in association with grasses, cereals and other non-nodulating crops. Virtually all of these bacteria are microaerophylic, fixing N₂ only in the presence of low partial pressures of oxygen. Until a few years ago much attention was focussed on members the genusAzospirillum and it was assumed that N₂ fixation was restricted to the rhizosphere or rhizoplane of the host plants. Through the use of N balance and¹⁵N techniques it has been shown that in the case of lowland rice, several tropical pasture grasses and especially sugar cane, the contributions of biological N₂ fixation (BNF) are of agronomic significance.More detailed study of the N₂-fixing bacteria associated with sugar cane (Acetobacter diazotrophicus andHerbaspirillum spp.) has shown that they occur in high numbers not only in roots of this crop but also in the stems, leaves and trash but are rarely found in the soil. Some of these endophytic diazotrophs have now also been found in forage grasses, cereals, sweet potato and cassava, although evidence of significant BNF contributions is still lacking.The identification of these endophytic diazotrophs as the organisms probably responsible for the high contributions of N₂ fixation observed in sugar cane suggests that it may be possible to attain significant BNF contributions in some other gramineae and perhaps root crops.     

双歧因子"宴会醋"的小型生产

双歧因子“宴会醋”是以苹果汁为原料,经醋酸菌发酵酿造果醋添加异麦芽低聚糖制成。成品具有保健功能,如调节人体菌群失调,降低血脂,保护肝脏以及润肠通便等,是一种包装新颖的多用途保健调味品。     

Modeling for local dynamic behaviors of phenol biodegradation in bubble columns

A coupled three-dimensional (3-D) model, combining hydrodynamics with biochemical reactions, was developed to simulate the local transient flow patterns and the dynamic behaviors of cell growth and phenol biodegradation by yeast Candida tropicalis in the bubble-column bioreactor, using the computational fluid dynamic (CFD) method. In order to validate this proposed model effectively, the validation of the local hydrodynamic characteristics of the gas-mineral salt solution (gas-liquid) two-phase system, with the phenol concentration of 1200 mg/L, and with the absence of cells, was performed in a square-sectioned bubble column bioreactor using the LDA system and conductivity probe. Furthermore, the validation of phenol biodegradation behaviors by yeast Candida tropicalis at different initial concentrations of phenol and cell was also carried out in the above bubble-column bioreactor. The results indicated that the model simulations had a satisfying agreement with the experimental data. Finally, the local instantaneous flow and phenol biodegradation features including gas holdup, gas velocity, liquid velocity, cell concentration and phenol concentration inside the bioreactor were successfully predicted in different-scale bubble columns by the proposed model. © 2006 American Institute of Chemical Engineers AIChE J, 2006