微生物法生产1,3-二羟基丙酮代谢工程研究进展

1,3-二羟基丙酮是一种重要的化工原料和医药中间体,广泛应用于化妆品、医药、食品等领域。以下综述了微生物法生产1,3-二羟基丙酮的代谢途径和关键酶,以及微生物法生产1,3-二羟基丙酮所涉及的代谢工程技术的研究进展。指出利用基因工程的方法对菌株进行改造,提高甘油脱氢酶催化活性,同时根据菌株的代谢特性,对发酵过程进行调控,提高1,3-二羟基丙酮的得率,是今后的研究方向。     

菜籽粕制备复合氨基酸螯合铜的工艺优化

发酵工艺已成功开发并用于生产大部分必需氨基酸,但蛋氨酸却是例外.尽管已经尝试利用微生物法生产蛋氨酸,但至今未能实现商业化生产.本文详细讨论了大肠杆菌、棒状杆菌和短杆菌等有潜在产蛋氨酸能力的菌株体内的蛋氨酸生物合成调节机制,阐述了微生物发酵法产蛋氨酸的研究进展,对蛋氨酸发酵生产的发展前景进行了展望.     

生物技术生产丁酸的研究进展

丁酸作为一种重要的化工原料,已经广泛应用于食品添加剂与医药等领域。目前,工业上生产丁酸主要是从石油中提取有机化合物进行化学合成。与有机化合物合成法相比,微生物发酵产丁酸的优势有：所用的原料来源非常广,发酵过程低能耗,不污染环境,而且可以持续添加原料发酵生产丁酸。因此,通过生物技术发酵生产丁酸越来越受到人们的重视。介绍了丁酸的性质、产丁酸菌株的特点、微生物发酵产丁酸的细胞代谢途径及其调控、发酵法生产丁酸的工艺运行方式和产丁酸菌株及其代谢产物的生理功能这五部分内容,以期为今后开展发酵法产丁酸的微生物基因工程改造以及生产工艺的优化提供参考。     

生物发酵法生产1,3-丙二醇和2,3-丁二醇

1,3-丙二醇(1,3-PDO)和2,3-丁二醇(2,3-BDO)是工业生产中常见的二醇,可以直接由可再生原料经生物转化生成,在化学、能源等方面具有广泛的用途。本文综述并讨论了微生物发酵法生产这两种二醇的进展,重点介绍了生产菌株的改造及发酵过程的优化。     

丁醇的生物炼制及研究进展

丁醇因其优越的燃烧性能成为目前最具研发前景的生物燃料之一,它通常以可再生资源为原料,经丙酮-丁醇-乙醇(ABE)发酵获得。尽管ABE发酵曾是最古老的大规模发酵工艺之一,但由于原料成本高,发酵液中丁醇浓度低以及较高浓度的丙酮、乙醇和有机酸等副产物积累等问题,导致丁醇的生物炼制仍然不具有经济竞争力。本文中,笔者从原料选择、原料预处理、纤维素酶酶解和丁醇发酵4个方面介绍丁醇生物炼制的基本流程以及相关研究,以进一步分析丁醇生产的主要瓶颈,并从生产菌株改造和丁醇分离2个方面总结近年来的相关研究进展。最后,讨论了未来丁醇生产研究的重点并指出菌株改造的方向。     

利用发酵法生产氨基葡萄糖的研究进展

氨基葡萄糖(GlcN)是一种重要的氨基己糖。它由葡萄糖的一个羟基被氨基取代形成,能够有效作用于软骨组织治疗风湿性关节炎,并被视为天然无害的食品及保健品配料,市场应用前景广阔。目前,生产GlcN的方法主要有酸水解法、酶解法及微生物发酵法。由于酸水解法及酶解法生产GlcN会对环境造成不利影响及生产效率低等原因,微生物发酵法生产GlcN得到了越来越多研究者的关注。对微生物代谢产GlcN的合成途径、霉菌发酵产GlcN及工程菌发酵产GlcN等方面进行了概述,并对微生物发酵法生产GlcN的研究方向进行了展望。     

微生物发酵生产虾青素

对微生物发酵法生产虾青素的微生物菌种、生物合成代谢途径、发酵工艺条件优化和提取分离检测方法等方面的研究现状进行了综述 ,并展望了微生物发酵法生产虾青素的前景。     

微生物发酵法生产1,3-丙二醇的研究新进展

1,3-丙二醇(1,3-PD)是一种重要的化工原料,广泛应用于医药、化工、食品及化妆品等行业,同时1,3-PD是合成聚对苯二甲酸丙二酯(PTT)的重要单体,市场需求量逐年增多。基于生态友好型、生产安全和可持续发展的要求,利用微生物转化可再生资源来生产1,3-PD受到了人们的广泛重视。综述了微生物发酵法生产1,3-PD的菌株、代谢途径、发酵和下游分离工艺及其新进展,并对工业生产中利用生物技术生产1,3-PD的未来前景和挑战进行了探讨。     

豆粕发酵制备大豆肽菌株的筛选

微生物发酵豆粕可以降解大豆蛋白为大豆肽,试验以蛋白酶活力和水解度为指标,结合液体发酵和固体发酵工艺考察菌株的发酵能力,从而筛选优良的豆粕发酵菌株。结果表明,通过初筛和复筛获得3株能较好发酵豆粕的芽胞菌菌株,为豆粕发酵工艺的研究奠定了基础。     

微生物发酵生产虾青素

对微生物发酵法生产虾青素的微生物菌种、生物合成代谢途径、发酵工艺条件优化和提取分离检测方法等方面的研究现状进行了综述,并展望了微生物发酵法生产虾青素的前景。     

Microbial production of dihydroxyacetone

Dihydroxyacetone is extensively used in cosmetic industry as an artificial suntan besides having clinical and biological applications. Thus, it is important to meet the commercial demand of dihydroxyacetone at an economical and qualitative level. Microbial route of production is found to be more favorable for dihydroxyacetone as compared to chemical methods. This review gives detailed information about the microbial route of dihydroxyacetone production. Till date the microorganism which is most utilized for dihydroxyacetone production is Gluconobacter oxydans. Some limitations associated with dihydroxyacetone production by G. oxydans like substrate inhibition, product inhibition and oxygen limitation are discussed here. Various fermentation modes and culture conditions have been tried for their ability to overcome these limitations. It has been found that fed-batch mode of fermentation provides a better yield as compared to batch mode for dihydroxyacetone production. Two-stage repeated fed-batch mode of fermentation has been found to be the most optimized mode. Immobilization has also been recognized as a much better alternative for fermentation since it avoids the problem of substrate and product inhibition to a greater extent. Although these methods have increased the dihydroxyacetone production to a prominent level yet the production has not reached the level required to meet the commercial demand. One looks for future prospects of developing recombinant microbial method for dihydoxyacetone production.     

利用生物柴油副产物粗甘油生产二羟基丙酮

以来自餐饮废油的生物柴油副产物粗甘油作为廉价底物,对弗托氏葡糖杆菌(Gluconobacter frateurii)CGMCC5397发酵转化生产二羟基丙酮(DHA)进行初步研究。研究发现粗甘油中的金属离子,尤其是Zn2+对微生物转化生产二羟基丙酮有明显抑制作用。粗甘油经过预处理后,利用优化后的发酵培养基,在7 L发酵罐中进行补料分批发酵,48 h后DHA浓度达到89.5 g/L,生产强度为1.86 g/(L·h),甘油转化率为90.1%。本研究初步证明了弗托氏葡糖杆菌能高效和经济地利用生物柴油副产物粗甘油生产DHA。     

Fermentative production of L-glycerol 3-phosphate utilizing a Saccharomyces cerevisiae strain with an engineered glycerol biosynthetic pathway

Interest in L-glycerol 3-phosphate (L-G3P) production via microbial fermentation is due to the compound's potential to replace the unstable substrate dihydroxyacetone phosphate (DHAP) in one-pot enzymatic carbohydrate syntheses. A Saccharomyces cerevisiae strain with deletions in both genes encoding specific L-G3Pases (GPP1 and GPP2) and multicopy overexpression of L-glycerol 3-phosphate dehydrogenase (GPD1) was studied via small-scale (100 mL) batch fermentations under quasi-anaerobic conditions. Intracellular accumulation of L-G3P reached extremely high levels (roughly 200 mM) but thereafter declined. Extracellular L-G3P was also detected and its concentration continuously increased throughout the fermentation, such that most of the total L-G3P was found outside the cells as fermentation concluded. Moreover, in spite of the complete elimination of specific L-G3Pase activity, the strain showed considerable glycerol formation suggesting unspecific dephosphorylation as a mechanism to relieve cells of intracellular L-G3P accumulation. Up-scaling the process employed fed-batch fermentation with repeated glucose feeding, plus an aerobic growth phase followed by an anaerobic product accumulation phase. This produced a final product titer of about 325 mg total L-G3P per liter of fermentation broth.     

Bioreactors for succinic acid production processes

Succinic acid (SA) has been recognized as one of the most important bio-based building block chemicals due to its numerous potential applications. Fermentation SA production from renewable carbohydrate feedstocks can have the economic and sustainability potential to replace petroleum-based production in the future, not only for existing markets, but also for new larger volume markets. Design and operation of bio-reactors play a key role. During the last 20 years, many different fermentation strategies for SA production have been described in literature, including utilization of immobilized biocatalysts, integrated fermentation and separation systems and batch, fed-batch, and continuous operation modes. This review is an overview of different fermentation process design developed over the past decade and provides a perspective on remaining challenges for an economically feasible succinate production processes. The analysis stresses the idea of improving the efficiency of the fermentation stage by improving bioreactor design and by increasing bioreactor performance.     

1,3-Propanediol production by Escherichia coli expressing genes from the Klebsiella pneumoniae dha regulon.

The dha regulon in Klebsiella pneumoniae enables the organism to grow anaerobically on glycerol and produce 1,3-propanediol (1,3-PD). Escherichia coli, which does not have a dha system, is unable to grow anaerobically on glycerol without an exogenous electron acceptor and does not produce 1,3-PD. A genomic library of K. pneumoniae ATCC 25955 constructed in E. coli AG1 was enriched for the ability to grow anaerobically on glycerol and dihydroxyacetone and was screened for the production of 1,3-PD. The cosmid pTC1 (42.5 kb total with an 18.2-kb major insert) was isolated from a 1,3-PD-producing strain of E. coli and found to possess enzymatic activities associated with four genes of the dha regulon: glycerol dehydratase (dhaB), 1,3-PD oxidoreductase (dhaT), glycerol dehydrogenase (dhaD), and dihydroxyacetone kinase (dhaK). All four activities were inducible by the presence of glycerol. When E. coli AG1/pTC1 was grown on complex medium plus glycerol, the yield of 1,3-PD from glycerol was 0.46 mol/mol. The major fermentation by-products were formate, acetate, and D-lactate. 1,3-PD is an intermediate in organic synthesis and polymer production. The 1,3-PD fermentation provides a useful model system for studying the interaction of a biochemical pathway in a foreign host and for developing strategies for metabolic pathway engineering.     

1,3-Propanediol production by Escherichia coli expressing genes from the Klebsiella pneumoniae dha regulon.

The dha regulon in Klebsiella pneumoniae enables the organism to grow anaerobically on glycerol and produce 1,3-propanediol (1,3-PD). Escherichia coli, which does not have a dha system, is unable to grow anaerobically on glycerol without an exogenous electron acceptor and does not produce 1,3-PD. A genomic library of K. pneumoniae ATCC 25955 constructed in E. coli AG1 was enriched for the ability to grow anaerobically on glycerol and dihydroxyacetone and was screened for the production of 1,3-PD. The cosmid pTC1 (42.5 kb total with an 18.2-kb major insert) was isolated from a 1,3-PD-producing strain of E. coli and found to possess enzymatic activities associated with four genes of the dha regulon: glycerol dehydratase (dhaB), 1,3-PD oxidoreductase (dhaT), glycerol dehydrogenase (dhaD), and dihydroxyacetone kinase (dhaK). All four activities were inducible by the presence of glycerol. When E. coli AG1/pTC1 was grown on complex medium plus glycerol, the yield of 1,3-PD from glycerol was 0.46 mol/mol. The major fermentation by-products were formate, acetate, and D-lactate. 1,3-PD is an intermediate in organic synthesis and polymer production. The 1,3-PD fermentation provides a useful model system for studying the interaction of a biochemical pathway in a foreign host and for developing strategies for metabolic pathway engineering.     

Influence of biomass degradation products on the fermentation of glucose to ethanol by Saccharomyces carlsbergensis W 34

Summary The experiments on the fermentation of glucose to ethanol were carried out using the yeast Saccharomyces carlsbergensis W 34. The fermentation time could be reduced to 6 hours. Biomass degradation products such as cellobiose, dihydroxyacetone, glyceraldehyde, showed no or little effect on the fermentation rate. Hydroxymethylfurfural, furfural, methylglyoxal and lignin compounds such as phenol and vanillin inhibit the fermentation in the 1 to 10 mg/mL range very decisively.     

Substrate and product inhibition of hydrogen production by the extreme thermophile,Caldicellulosiruptor saccharolyticus

Substrate and product inhibition of hydrogen production during sucrose fermentation by the extremely thermophilic bacterium Caldicellulosiruptor saccharolyticus was studied. The inhibition kinetics were analyzed with a noncompetitive, nonlinear inhibition model. Hydrogen was the most severe inhibitor when allowed to accumulate in the culture. Concentrations of 5-10 mM H(2) in the gas phase (identical with partial hydrogen pressure (pH(2)) of (1-2) x 10(4) Pa) initiated a metabolic shift to lactate formation. The extent of inhibition by hydrogen was dependent on the density of the culture. The highest tolerance for hydrogen was found at low volumetric hydrogen production rates, as occurred in cultures with low cell densities. Under those conditions the critical hydrogen concentration in the gas phase was 27.7 mM H(2) (identical with pH(2) of 5.6 x 10(4) Pa); above this value hydrogen production ceased completely. With an efficient removal of hydrogen sucrose fermentation was mainly inhibited by sodium acetate. The critical concentrations of sucrose and acetate, at which growth and hydrogen production was completely inhibited (at neutral pH and 70 degrees C), were 292 and 365 mM, respectively. Inorganic salts, such as sodium chloride, mimicked the effect of sodium acetate, implying that ionic strength was responsible for inhibition. Undissociated acetate did not contribute to inhibition of cultures at neutral or slightly acidic pH. Exposure of exponentially growing cultures to concentrations of sodium acetate or sodium chloride higher than ca. 175 mM caused cell lysis, probably due to activation of autolysins.     

Improvement of 1,3-dihydroxyacetone production from Gluconobacter oxydans by ion beam implantation

Improvement of dihydroxyacetone (DHA) production by mutagenesis of ion beam implantation and medium optimization using response-surface methodology (RSM) were investigated in this work. More than 1000 mutant strains were selected through a mutagenesis method using N(+) ions implantation with a dose of 60?×?(2.6?×?10(13)) ions/cm(2) and energy of 10?keV. Several high-yield mutant strains were showed the potent application for DHA production and the genetically stable mutant strain G. oxydans ZJB09113 was selected for optimization of cultivation condition by RSM. The optimal medium for DHA fermentation is composed (in g/L) of yeast extract 4.88, CaCO(3) 2.00, and glycerol 52.86?mL/L (initial pH 4.89). The maximal DHA concentration of 40.0?g/L was achieved after 24?hr of shaken flask fermentation at 30°C with 150?rpm, and 196.3% increase in DHA production in comparison with unoptimized conditions.