Fermentation at non-conventional conditions in food- and bio-sciences by the application of advanced processing technologies

The interest in improving the yield and productivity values of relevant microbial fermentations is an increasingly important issue for the scientific community. Therefore, several strategies have been tested for the stimulation of microbial growth and manipulation of their metabolic behavior. One promising approach involves the performance of fermentative processes during non-conventional conditions, which includes high pressure (HP), electric fields (EF) and ultrasound (US). These advanced technologies are usually applied for microbial inactivation in the context of food processing. However, the approach described in this study focuses on the use of these technologies at sub-lethal levels, since the aim is microbial growth and fermentation under these stress conditions. During these sub-lethal conditions, microbial strains develop specific genetic, physiologic and metabolic stress responses, possibly leading to fermentation products and processes with novel characteristics. In some cases, these modifications can represent considerable improvements, such as increased yields, productivities and fermentation rates, lower accumulation of by-products and/or production of different compounds. Although several studies report the successful application of these technologies during the fermentation processes, information on this subject is still scarce and poorly understood. For that reason, the present review paper intends to assemble and discuss the main findings reported in the literature to date, and aims to stimulate interest and encourage further developments in this field.     

Genetic improvement of processes yielding microbial products

Although microorganisms are extremely good in presenting us with an amazing array of valuable products, they usually produce them only in amounts that they need for their own benefit; thus, they tend not to overproduce their metabolites. In strain improvement programs, a strain producing a high titer is usually the desired goal. Genetics has had a long history of contributing to the production of microbial products. The tremendous increases in fermentation productivity and the resulting decreases in costs have come about mainly by mutagenesis and screening/selection for higher producing microbial strains and the application of recombinant DNA technology.     

生物酶法合成L-精氨酸衍生物的研究进展

L-精氨酸是一种碱性氨基酸,具有多样化的官能团,是合成多种有用化合物的前体,其衍生物广泛应用于医疗、食品和化妆品等领域。L-精氨酸衍生物的合成方法有化学法、发酵法和酶法。在当前绿色经济和可持续发展的背景下,对比各种生产方法,生物酶法合成L-精氨酸衍生物具有明显优势。因此本文重点介绍了L-精氨酸衍生化的典型产品和合成技术,并介绍了生物酶法合成L-精氨酸衍生物未来可能的发展方向。     

代谢工程改造酿酒酵母生产L-乳酸的研究进展

L-乳酸是一种重要的有机化合物,具有广泛的应用价值。微生物发酵法生产是当前L-乳酸的主要来源,但受限于精确的发酵条件、菌体产物耐受能力低及底物要求高等因素,导致L-乳酸供给不足且价格偏高。鉴于酿酒酵母利用廉价底物生产有价值物质方面的诸多优势,并随着分子生物学技术的发展,利用代谢工程改造酿酒酵母本身固有的代谢网络,使其高产L-乳酸已成为当前研究的热点。从L-乳酸的异源生产、关键途径改造及菌体生长能力恢复三个方面归纳了关于代谢工程改造酿酒酵母生产L-乳酸的研究进展。最后,指出了酿酒酵母异源生产L-乳酸存在的不足和今后研究的方向。     

Microbial production of 1,3-propanediol: Recent developments and emerging opportunities

1,3-Propanediol, a valuable bifunctional molecule, can be produced from renewable resources using microorganisms. It has several promising properties for many synthetic reactions, particularly for polymer and cosmetic industries. By virtue of being a natural product, relevant biochemical pathways can be harnessed into fermentation processes to produce 1,3-propanediol. Various strategies for the microbial production of 1,3-propanediol are reviewed and compared in this article with their promises and constraints. Furthermore, genetic and metabolic engineering could significantly improve product yields and overcome the limitations of fermentation technology. Present review gives an overview on 1,3-propanediol production by wild and recombinant strains. It also attempts to encompass the various issues concerned in utilization of crude glycerol for 1,3-propanediol production, with particular emphasis laid on biodiesel industries. This review also summarizes the present state of strategies studied for the downstream processing and purification of biologically produced 1,3-propanediol. The future prospect of 1,3-propanediol and its potential as a major bulk chemical are discussed under the light of the current research.     

燃料乙醇发酵技术研究进展

在分析木质纤维素类生物质制备燃料乙醇原理基础上,重点对燃料乙醇转化过程的发酵工艺进行了论述。目前乙醇发酵工艺主要包括直接发酵、分步糖化发酵、同步糖化发酵、同步糖化共发酵和联合生物加工技术等,对这几种技术的研究现状进行了分析并对其发展趋势进行了展望,通过基因工程构建高效发酵菌种的联合生物加工技术将是未来高效发酵工艺的发展趋势,旨在为有效提高发酵菌株的底物代谢能力,获得高的乙醇产量提供重要参考。     

工业微生物：创新与突破专刊序言(2021)

工业微生物及其产品广泛用于工业、农业、医药等诸多领域,相关产业在国民经济中具有举足轻重的地位。高效的菌株是提高生产效率的核心,而先进发酵技术和仪器平台对充分开发菌株代谢潜能也很重要。近年来,工业微生物领域的研究取得了快速进展,人工智能、高效基因组编辑技术和合成生物学技术逐渐广泛使用,相关产业应用也在不断扩展。为进一步促进工业微生物在生物制造等领域的应用,《生物工程学报》特组织出版专刊,从微生物菌株的多样性和生理代谢、菌株改造技术、发酵过程优化和放大,高通量微液滴培养装备开发以及工业微生物应用等方面,分别阐述目前的研究进展,并展望未来的发展趋势,为促进工业微生物及生物制造等产业的发展奠定基础。     

Whole microbial cell processes for manufacturing amino acids, vitamins or ribonucleotides

The development of recombinant DNA technology has greatly expanded whole microbial cell processes for manufacturing amino acids, vitamins, or ribonucleotides. A novel well-designed scheme with integrated enzymatic conversions and fermentation enables the production of even complicated compounds, such as sugar nucleotides and oligosaccharides.     

S-腺苷甲硫氨酸的研究进展

S-腺苷甲硫氨酸(SAM)是甲硫氨酸和三磷酸腺苷相结合的代谢物,广泛存在于动植物和微生物体内,参与40多种生化反应,主要作为三种代谢途径(转甲基、转硫基、转氨丙基)的前体,临床上被广泛用于治疗肝病、抑郁症、关节炎等。SAM的制备方法主要有化学合成法、酶促合成法、发酵法三种。化学合成的SAM是消旋体,需进行光学拆分,且存在产率低、原料L-高半胱氨酸价格昂贵和环境污染等问题。酶促合成法合成的SAM纯度高,但原料ATP成本太高。发酵法已成为目前生产SAM最常用的方法,欧洲利用发酵法生产SAM已实现了产业化,但国内的起步较晚,目前还处于实验室研究阶段。因此,应加强发酵法生产SAM的产业化关键技术研究。     

Metabolomics: quantification of intracellular metabolite dynamics

The rational improvement of microbial strains for the production of primary and secondary metabolites ('metabolic engineering') requires a quantitative understanding of microbial metabolism. A process by which this information can be derived from dynamic fermentation experiments is presented. By applying a substrate pulse to a substrate-limited, steady state culture, cellular metabolism is shifted away from its metabolic steady state. With the aid of a rapid sampling and quenching routine it is possible to take 4-5 samples per second during this process, thus capturing the metabolic response to this stimulus. Over 30 metabolites, nucleotides and cofactors from Escherichia coli metabolism can be extracted and analysed using a range of different techniques, for example enzymatic assays, HPLC and LC-MS methods. Using different substrates as limiting and pulse-substrates (glucose, glycerol), different metabolic pathways and substrate uptake systems are investigated. The resulting plots of intracellular metabolite concentrations against time serve as a data basis for modelling microbial metabolic networks.     

微生物发酵床养猪技术研究进展

微生物发酵床养猪模式是一种新型的低能耗、环保健康养殖方式。本文从微生物发酵床养猪技术原理、垫料的组成与管理技术、垫料微生物群落结构、对病原微生物的抑制作用、挥发性物质以及用后垫料资源化利用技术等方面综述了国内微生物发酵床养猪技术进展,分析了该技术推广应用中存在的问题,并提出构建微生物发酵床垫料资源化利用体系作为今后重点研究与发展方向。     

Molecular Adaptation Mechanisms Employed by Ethanologenic Bacteria in Response to Lignocellulose-derived Inhibitory Compounds

Current international interest in finding alternative sources of energy to the diminishing supplies of fossil fuels has encouraged research efforts in improving biofuel production technologies. In countries which lack sufficient food, the use of sustainable lignocellulosic feedstocks, for the production of bioethanol, is an attractive option. In the pre-treatment of lignocellulosic feedstocks for ethanol production, various chemicals and/or enzymatic processes are employed. These methods generally result in a range of fermentable sugars, which are subjected to microbial fermentation and distillation to produce bioethanol. However, these methods also produce compounds that are inhibitory to the microbial fermentation process. These compounds include products of sugar dehydration and lignin depolymerisation, such as organic acids, derivatised furaldehydes and phenolic acids. These compounds are known to have a severe negative impact on the ethanologenic microorganisms involved in the fermentation process by compromising the integrity of their cell membranes, inhibiting essential enzymes and negatively interact with their DNA/RNA. It is therefore important to understand the molecular mechanisms of these inhibitions, and the mechanisms by which these microorganisms show increased adaptation to such inhibitors. Presented here is a concise overview of the molecular adaptation mechanisms of ethanologenic bacteria in response to lignocellulose-derived inhibitory compounds. These include general stress response and tolerance mechanisms, which are typically those that maintain intracellular pH homeostasis and cell membrane integrity, activation/regulation of global stress responses and inhibitor substrate-specific degradation pathways. We anticipate that understanding these adaptation responses will be essential in the design of ''intelligent'' metabolic engineering strategies for the generation of hyper-tolerant fermentation bacteria strains.     

微生物发酵法生产L-色氨酸的代谢工程研究

L-色氨酸作为人体内的一种必需氨基酸,广泛应用于医药、食品与饲料等行业.工业上采用的色氨酸生产方法有化学合成法、转化法及微生物发酵法.近年来,随着代谢工程在色氨酸菌种选育中的成功运用,微生物发酵法逐渐成为主要的色氨酸生产方法.系统综述了微生物发酵法生产色氨酸所涉及的代谢工程策略,包括生物合成色氨酸的代谢调控机制以及途径...     

微生物油脂的研究进展及展望

综述了培养微生物生产油脂的发展历史及研究现状,讨论了产油影响因素,对于其瓶颈因素碳源和氮源的影响。可采用培养后期限制氮源并补加碳源的措施,从而解决增加微生物油脂的含量。展望了采取微生物混合培养方法生产油脂技术研究的发展前景。     

Mushrooms: Potential protein source from cellulosic residues

Lignocelluloses are the most abundant organic renewable raw materials, with about 10–15 tons per capita produced annually by plants, available for microbial or other conversions. Although mushroom culture is one of the oldest microbial foods of man and the first solid-state fermentation, the basic research of microbial technology has not been applied to any significant extent to mushroom cultivation. In fact, the only means for converting unmodified lignocellulosics biologically is through the production of various edible mushrooms, which are regarded as a great delicacy. The cultivation techniques of various edible mushrooms and their nutritive values are reviewed in this paper.     

微生物发酵饲料在绿色养殖中应用的研究进展

微生物发酵饲料，目前是饲料工业和养殖业的关注热点之一，也是绿色安全养殖的重要条件。我国早在20世纪90年代开始研究。近年来，微生物发酵饲料在畜牧业生产中得到迅速发展，其生产和应用形式更加多样化。在水产畜牧养殖时，将日基础饲粮部分替换成微生物发酵饲料或经复合微生物发酵后直接饲用，因含有活菌及相关代谢产物，能进一步改善动物对饲料的营养吸收、提高动物的生产性能、防病治病和改善养殖环境。未来将在饲料替代抗生素、饲养高品质动物、畜禽防病等方面发挥必不可少的作用。本文阐释了微生物发酵饲料概念，作用机理及其在畜牧业、水产养殖应用中的最新研究现状，为微生物发酵饲料产品及新技术的研发提供参考。     

微生物基因功能的研究策略与方法

微生物基因功能的研究对于揭示微生物生命活动的规律及其在食品发酵、医药卫生、工农业生产等领域的应用机制具有重要意义。经过数十年的发展,微生物基因功能的研究方法已经从传统的同源重组技术发展到基于核酸内切酶的高效打靶技术,将微生物基因功能的研究推向了新的高度。文章就微生物基因功能的研究策略及常用方法做一综述,主要包括生物信息学方法预测、基因表达谱分析、基因敲除技术、基因敲入技术、基因沉默技术和基因编辑技术等。     

Metabolic flux network and analysis of fermentative hydrogen production

Fermentative hydrogen production (FHP) has received a great R & D interest in recent decades, as it offers a potential means of producing H₂ from a variety of renewable resources, even wastewater via a low energy continuous process. Various extracellular metabolites including ethanol, acetate, butyrate and lactate can be produced during the fermentation, building a complex metabolic network of the FHP. Except for the recognition of its complexity, the metabolic flux network has not been well understood. Studies on biochemical reactions and metabolic flux network associated with the FHP in anaerobic fermentation system have only been drawn attention in recent years. This review summarizes the biochemical reactions taking place in the metabolic network of FHP. We discuss how the key operation factors influence metabolism in the FHP process. Recently developed and applied technologies for metabolic flux analysis have been described. Future studies on the metabolic network to enhance fermentative hydrogen production by strict anaerobes are recommended. It is expected that this review can provide useful information in terms of fundamental knowledge and update technology for scientists and research engineers in the field of biological hydrogen production.     

餐厨废弃物资源化利用的微生物技术研究进展

简单介绍餐厨废弃物的特征和危害,综述微生物技术处理餐厨废弃物资源化的途径,如发酵提取生物降解塑料技术、厌氧发酵处理技术、微生物堆肥技术、微生物农药技术、微生物产电技术,介绍利用复合微生物菌剂降解餐厨废弃物的研究进展,分析这一新技术的发展趋势。