Characterization and application of a recombinant dopa decarboxylase from Harmonia axyridis for the efficient biosynthesis of dopamine

Here,a dopa decarboxylase (DDC) from Harmonia axyridis was heterogeneously expressed in Escherichia coli for the efficient biosynthesis of dopamine.For the production of recombinant DDC,the cultivation conditions including IPTG concentration,temperature and induction time were optimized and obtained an optimal specific enzyme activity of 51.72 U·mg-1 crude extracts.After the purification of DDC with a recovery yield of 68.79％,its activity was further characterized.The Vmax,Km,Kcat,and Kcat/Km of DDC for dihydroxyphenylalanine (dopa) were 0.02 mmol·ml-1·s-1,2.328 mmol·ml-1,10435.90 s-1 and 4482.77 ml·mmol-1·s-1,respectively.The highest DDC activity was observed at the condition of pH 7.5 and 45 ℃.With the purified DDC,the feasibility to produce dopamine from L-dopa was evaluated.The optimal yield was determined at the following bioconversion conditions:pH of 7.0,the reaction temper-ature of 40 ℃,0.4 mmol·L-1 of PLP and 4 g·L-1 of L-dopa.Subsequently,a fed-batch process for the pro-duction of dopamine was developed and the effect of oxygen was evaluated.The titer,yield and productivity of dopamine reached up to 21.99 g·L-1,80.88％ and 14.66 g·L-1h-1 at 90 min under anaer-obic condition.     

表面活性剂在生物转化法合成普鲁兰中的作用及生理机制

考察斯潘类和吐温类表面活性剂在利用出芽短梗霉全细胞生物转化合成普鲁兰多糖中的作用,结果发现20 g/L斯潘80和5 g/L吐温80将细胞的普鲁兰合成能力分别提高了46.5%和32.9%,二者复配使用进一步提高了普鲁兰产量和合成效率。通过对相关生理生化参数进行测定,发现斯潘80和吐温80增加了细胞膜的通透性,提高了普鲁兰合成关键酶的活性,提升了胞内尿苷二磷酸葡萄糖和能量物质ATP的水平,加速了ATP的再生,在促进物质和能量代谢的基础上,实现了普鲁兰产量和合成效率的提高。研究结果部分解析了表面活性剂提高普鲁兰合成效率的生理机制,同时也为其他类似结构微生物多糖的高效合成提供技术参考。     

Biovanillin from agro wastes as an alternative food flavour

This review provides an overview of biovanillin production from agro wastes as an alternative food flavour. Biovanillin is one of the widely used flavour compounds in the foods, beverages and pharmaceutical industries. An alternative production approach for biovanillin as a food flavour is hoped for due to the high and variable cost of natural vanillin as well as the limited availability of vanilla pods in the market. Natural vanillin refers to the main organic compound that is extracted from the vanilla bean, as compared to biovanillin, which is produced biologically by microorganisms from a natural precursor such as ferulic acid. Biovanillin is also reviewed as a potential bioflavour produced by microbial fermentation in an economically feasible way in the near future. In fact, we briefly discuss natural, synthetic and biovanillin and the types of agro wastes that are useful as sources for bioconversion of ferulic acid into biovanillin. The subsequent part of the review emphasizes the current application of vanillin as well as the utilization of biovanillin as an alternative food flavour. The final part summarizes biovanillin production from agro wastes that could be of benefit as a food flavour derived from potential natural precursors.© 2012 Society of Chemical Industry     

Monoterpene alcohols release and bioconversion by Saccharomyces species and hybrids

Terpene profile of Muscat wines fermented by Saccharomyces species and hybrid yeasts was investigated. The amount of geraniol decreased in most wines with respect to the initial must except for Saccharomyces bayanus wines. On the other hand, alpha-terpineol amount was higher in wines fermented by Saccharomyces cerevisiae and hybrid yeasts. The amount of linalool was similar in all wines and comparable to the amount in the initial must. Lower levels of beta-d-glucosidase activity were found in the hybrid yeasts with respect to S. cerevisiae. Moreover, no relationship between beta-d-glucosidase activity and terpenes profile in Muscat wines fermented with Saccharomyces species and hybrids was found. Growth of yeasts on minimum medium supplemented with geraniol showed bioconversion of geraniol into linalool and alpha-terpineol. Percentages of geraniol uptake and bioconversion were different between Saccharomyces species and hybrids. Strains within S. bayanus, Saccharomyces kudriavzevii and hybrids showed higher geraniol uptake than S. cerevisiae, whereas the percentage of produced linalool and alpha-terpineol was higher in S. cerevisiae and hybrid yeasts than in S. bayanus and S. kudriavzevii. The relationship between geraniol uptake and adaptation of Saccharomyces species to grow at low temperature is discussed.     

植物乳杆菌转化合成共轭亚油酸的培养基条件优化

生物法转化合成共轭亚油酸,产物中异构体组成单一,具有很好的应用前景。通过一株植物乳杆菌(Lactobacillus plantarum)合成共轭亚油酸的培养基成分进行优化,确定最优的培养基组成:葡萄糖20g/L,酵母浸出物40g/L,硫酸镁0.5g/L,硫酸锰0.5g/L,乙酸钠2g/L,磷酸氢二钾1g/L。优化后,共轭亚油酸产量达到0.259g/L,相比优化前(0.0455g/L)有了较大的提升。      

雄烯二酮转化菌的复合诱变及性能检测

生物转化法生产雄烯二酮还未实现大规模工业化生产的主要原因之一是雄烯二酮转化率低。以Mycobac-teriumsp.BD696#为出发菌株，分别采用UV照射、^60Co照射、UV＋^60Co复合诱变处理筛选获得一株高转化率突变株SP-UC-8#。其产生AD的能力较出发菌株提高了39.2%，且不再产生结构类似物雄二烯二酮（ADD），且传至第五代产率仍较为稳定，说明UV＋^60Co复合诱变是遗传育种的一种有效方法。     

我国水果副产物综合利用的研究及应用

随着水果种植面积和加工规模不断扩大,我国水果副产物资源也越来越多,由此引发的资源浪费和环境污染的问题也越来越严重。在水果生产过程中,果园中的落果、残次果以及不可直接食用的根茎叶等资源的浪费给果农造成了相当大的经济损失。水果加工后剩余的果皮、果渣、果核、种籽、叶、茎、根等下脚料以及加工废水等如果不加以综合利用,不仅会造成资源浪费,还会增加加工企业的废渣废水处理成本。本文阐述了水果副产物的含义及其综合利用研究进展,分析水果副产物利用存在的问题和发展趋势。     

脂肪酸微生物转化生产羟基脂肪酸的研究进展

羟基脂肪酸是一种在生物可降解聚合物材料、化工、食品及机械等行业具有十分重要用途的化合物：对天然底物脂肪酸通过微生物转化方法生产羟基脂肪酸所涉及的微生物种类、微生物转化的作用机理和发酵条件等,特别是转化脂肪酸生产ω-1、ω-2和ω-3-羟基脂肪酸的细胞色素P450系统进行了较系统的分析和阐述,并对羟基脂肪酸的生产及发展趋势作了展望,为进一步研究和工业化生产羟基脂肪酸提供了基础。     

生物转化木质纤维素原料生产乳酸的研究进展

以木质纤维素生物原料转化生产乳酸对节约粮食、保护环境和促进乳酸产业的发展意义重大.对纤维素生产乳酸的几个技术环节:原料预处理、酶促水解、乳酸发酵的研究进展作了概要介绍和评述.并强调提高酶解效率和降低生产成本仍是现阶段研究的主要目标,指出各种新技术的集成与优化是加快其产业化进程的必由之路.