豆粕营养成分对蝙蝠蛾拟青霉发酵产物的影响

为探索培养基中的豆粕以及制备豆粕的原材料大豆对蝙蝠蛾拟青霉发酵产物的影响,我们比较了不同品种大豆和用其制成的豆粕的主要营养成分含量,包括粗蛋白、粗脂肪、6种微量元素（钙、镁、铜、锌、铁、锰）和总异黄酮（大豆苷、黄豆黄苷、染料木苷、大豆苷元、黄豆黄素、染料木素）,以及豆粕作为培养基对蝙蝠蛾拟青霉发酵产物的生物量和有效成分含量包括腺苷、腺嘌呤、虫草素和麦角甾醇的影响,结果表明大豆中钙和大豆苷与发酵产物中腺苷含量正相关。豆粕中钙、大豆苷、大豆苷元、染料木素与发酵产物中腺苷含量正相关;豆粕中钙、镁、大豆苷、大豆苷元、染料木素、总异黄酮与发酵产物中腺嘌呤含量负相关;豆粕中铁与菌丝体干重值正相关。结果表明,培养基中的豆粕和原料大豆主要营养成分含量对蝙蝠蛾拟青霉发酵产物品质有显著影响。     

Redox potential control and applications in microaerobic and anaerobic fermentations

Many fermentation products are produced under microaerobic or anaerobic conditions, in which oxygen is undetectable by dissolved oxygen probe, presenting a challenge for process monitoring and control. Extracellular redox potentials that can be detected conveniently affect intracellular redox homeostasis and metabolism, and consequently control profiles of fermentation products, which provide an alternative for monitoring and control of these fermentation processes. This article reviews updated progress in the impact of redox potentials on gene expression, protein biosynthesis and metabolism as well as redox potential control strategies for more efficient production of fermentation products, taking ethanol fermentation by the yeast Saccharomyces under microaerobic conditions and butanol production by the bacterium Clostridium under anaerobic conditions as examples.     

Comparison of solid-state and submerged-state fermentation for the bioprocessing of switchgrass to ethanol and acetate by Clostridium phytofermentans

The conversion of sustainable energy crops using microbiological fermentation to biofuels and bioproducts typically uses submerged-state processes. Alternatively, solid-state fermentation processes have several advantages when compared to the typical submerged-state processes. This study compares the use of solid-state versus submerged-state fermentation using the mesophilic anaerobic bacterium Clostridium phytofermentans in the conversion of switchgrass to the end products of ethanol, acetate, and hydrogen. A shift in the ratio of metabolic products towards more acetate and hydrogen production than ethanol production was observed when C. phytofermentans was grown under solid-state conditions as compared to submerged-state conditions. Results indicated that the end product concentrations (in millimolar) obtained using solid-state fermentation were higher than using submerged-state fermentation. In contrast, the total fermentation products (in weight of product per weight of carbohydrates consumed) and switchgrass conversion were higher for submerged-state fermentation. The conversion of xylan was greater than glucan conversion under both fermentation conditions. An initial pH of 7 and moisture content of 80 % resulted in maximum end products formation. Scanning electron microscopy study showed the presence of biofilm formed by C. phytofermentans growing on switchgrass under submerged-state fermentation whereas bacterial cells attached to surface and no apparent biofilm was observed when grown under solid-state fermentation. To our knowledge, this is the first study reporting consolidated bioprocessing of a lignocellulosic substrate by a mesophilic anaerobic bacterium under solid-state fermentation conditions.     

Production of Botrytis cinerea for potential introduction into a vineyard

Botrytis cinerea was produced in solid-phase fermentation, liquid fermentation and on potato dextrose agar. Stored products were evaluated for grape colonization in grape bioassays and in field trials, and for B. cinerea density using colony forming unit analyses and a nucleic-acid-based method. B. cinerea colony forming unit density was significantly correlated to the probability of successful grape colonization in grape bioassays (p-value=0.0002). Solid fermentation products could be stored longer than liquid fermentation and potato dextrose agar products. There was little difference in the rate of grape colonization in laboratory bioassays among solid-phase fermentation, liquid fermentation and plate culture products. Although the initial B. cinerea colonization rate of field grapes was slightly greater on vines treated with solid-phase fermentation and plate culture products compared to vines treated with product from liquid fermentation, there was no significant difference in final colonization between vines treated with solid-phase fermentation, liquid fermentation and plate culture products and untreated vines.     

灵芝真菌液体发酵及其产物应用的研究进展

灵芝作为一种白腐真菌,同时也是珍稀的食药用真菌,富含多种生物活性成分。液体发酵技术生产周期短、效率高、产量大、品质稳定,是开发利用灵芝资源的重要途径。近年来,灵芝属真菌菌丝体液体发酵技术的开发与应用取得了较大进展。本文对灵芝属真菌液体发酵产物的主要活性成分及其药用效果、液体发酵工艺优化和发酵产物的应用进行综述,并对本领域的未来进行展望。     

Butanol production from cellulosic substrates by sequential co-culture ofClostridium thermocellum andC.acetobutylicum

A sequential co-culture approach was investigated for the conversion of lignocellulosic substrates to fuels and chemicals. Growth ofClostridium acetobutylicum on solka floc (or a mixture of solka floc and aspenwood xylan), in co-culture withC.thermocellum, resulted in the efficient utilization of all the hydrolysis products derived from the lignocellulosic substrates. This co-culture approach resulted in a 1.7–2.6 fold increase in the total fermentation products formed. The majority of the fermentation products were acids and not solvents, however the solventogenesis step could be induced by the addition of butyric acid to the fermentation medium.     

Lessons from the cow: What the ruminant animal can teach us about consolidated bioprocessing of cellulosic biomass

Consolidated bioprocessing (CBP) of cellulosic biomass is a promising source of ethanol. This process uses anaerobic bacteria, their own cellulolytic enzymes and fermentation pathways that convert the products of cellulose hydrolysis to ethanol in a single reactor. However, the engineering and economics of the process remain questionable. The ruminal fermentation is a very highly developed natural cellulose-degrading system. We propose that breakthroughs developed by cattle and other ruminant animals in cellulosic biomass conversion can guide future improvements in engineered CBP systems. These breakthroughs include, among others, an elegant and effective physical pretreatment; operation at high solids loading under non-aseptic conditions; minimal nutrient requirements beyond the plant biomass itself; efficient fermentation of nearly all plant components; efficient recovery of primary fermentation end-products; and production of useful co-products. Ruminal fermentation does not produce significant amounts of ethanol, but it produces volatile fatty acids and methane at a rapid rate. Because these alternative products have a high energy content, efforts should be made to recover these products and convert them to other organic compounds, particularly transportation fuels.     

Influence of prebrining treatments on microbial and biochemical changes during the baceman stage in Indonesian kecap (soy sauce) production

Prior to the baceman stage or brine fermentation in Indonesian kecap (soy sauce) production, the soybeans undergo a number of treatments, such as soaking, cooking and a fungal solid state fermentation (bungkil stage). The influence of these prebrining steps on the baceman stage was investigated. Acidification during soaking inhibited bacterial growth during the solid state fermentation, causing lower initial numbers of bacteria in and a slower acidification of the baceman. Cooking time influenced the softness of the beans and thus fungal growth during the bungkil stage. Increasing the cooking time from 1 to 3 h resulted in a better solubility of macromolecules and gave higher final concentrations of fermentation products and formol nitrogen in baceman. When cooking time was increased from 3 to 5 h only slight differences could be observed. Length of the bungkil stage had some minor influences; the amount of fermentation products and residual monosaccharides decreased by 16% when the length was increased from 2 to 7 d. The highest amounts of formol nitrogen were found with 5 d of bungkil fermentation. The addition of rice flour showed that the absence of yeast fermentation in baceman is related to the lack of sugars after the previous lactic acid fermentation. In addition to yeast fermentation, the growth of fungi during the bungkil stage was also positively influenced by the addition of rice flour. Sun drying and crumbling bungkil caused lower enzyme activities and resulted in lower amounts of formol nitrogen and glycerol. Growth of Pediococcus halophilus during the baceman stage was faster when bungkil was sun dried, although the final concentrations of fermentation products were lower due to a lower content of amino acids which resulted in less buffering. Increasing the amount of bungkil added to salty water caused a similar increase in formol nitrogen and fermentation products.     

Cause analysis of the effects of acid-catalyzed steam-exploded corn stover prehydrolyzate on ethanol fermentation by Pichia stipitis CBS 5776

The prehydrolyzate obtained from acid-catalyzed steam-exploded corn stover (ASC) mainly contains xylose and a number of inhibitory compounds that inhibit ethanol fermentation by Pichia stipitis. In this study, the effects of the ASC prehydrolyzate, specifically those of the carbohydrate-degradation products, lignin-degradation products (which were extracted from ASC prehydrolyzate using ethyl acetate), and six major phenolic compounds (added to pure-sugar media individually or in combination), on ethanol fermentation were investigated. Results indicate that the effects of the carbohydrate-degradation products were negligible (10 h delayed) compared with those of pure-sugar fermentation, whereas the effects of the lignin-degradation products were significant (52 h delayed). Meanwhile, the inhibitory effects of the major phenolic compounds were not caused by certain types of inhibitors, but were due to the synergistic effects of various inhibitors.     

Fermentation for future food systems: Precision fermentation can complement the scope and applications of traditional fermentation

Modern biotechnology holds great potential for expanding the scope of fermentation to create novel foods and improve the sustainability of food production.

The growing human population and global warming pose an impending threat for global food security (Linder, 2019). This has prompted a critical re‐examination of the food supply chain from producers to consumers in order to increase the overall efficiency of food production, storage and transport. Much research in plant science consequently aims to increase production with new, high‐yield crop, fruit and vegetable varieties better adapted to changing climatic conditions. Yet, there is also much room for improving food safety by minimising food losses and recycling waste, valorising by‐products, improving nutritional value and increasing storage time. This is where fermentation comes in as a cost‐efficient, versatile and proven technology that extends the shelf life of food products and enhances their nutritional content. Moreover, there is enormous potential in fermentation to further increase efficiency and product range and even create new food products from non‐food biomass.

… there is enormous potential in fermentation to further increase efficiency and product range and even create new food products from non‐food biomass.

In a broader sense, fermentation can be defined as the cultivation of microorganisms such as bacteria, yeasts and fungi to break down complex molecules into simpler ones, notably organic acids, alcohols or esters. In a practical sense, it is one of the oldest food processing technologies to increase storage life along with cooking, smoking or air‐drying: fermentation was already fully industrialised for producing beer and bread millennia ago in ancient Mesopotamia and Egypt. It is also an elegant and simple technology as these microorganisms do most of the work without much human involvement.Louis Pasteur’s discovery that microorganisms cause fermentation laid the basis for further improvement of the technology from traditional spontaneous fermentation to the use of defined starter cultures. Fermentation is now widely used to produce alcoholic beverages, bread and pastry, dairy products, pickled vegetables, soy sauce and so on. More recent advances based on genomics and synthetic biology include precision and biomass fermentation to produce specific compounds for the food and chemical industry or medicinal use. This is not the limit though: when combined with genomics, fermentation has even greater potential for creating novel foods and other products.     

拉曼光谱分析技术在资源微生物发酵性能评价中的应用

微生物发酵过程是细胞新陈代谢进行物质转化的过程,为了提高目标产物的转化率,需要对微生物发酵动态特性进行实时分析,以便实时优化发酵过程。拉曼光谱(Raman spectroscopy)量化测试作为一种有应用前景的在线过程分析技术,可以在避免微生物污染的条件下,实现精准监测,进而用于优化控制微生物发酵过程。【目的】以运动发酵单胞菌(Zymomonas mobilis)为例,建立微生物发酵过程中葡萄糖、木糖、乙醇和乳酸浓度拉曼光谱预测模型,并进行准确性验证。【方法】采用浸入式在线拉曼探头,收集运动发酵单胞菌发酵过程中多个组分的拉曼光谱,采用偏最小二乘法对光谱信号进行预处理和多元数据分析,结合离线色谱分析数据,对拉曼光谱进行建模分析和浓度预测。【结果】针对运动发酵单胞菌,首先实现拉曼分析仪对单一产品乙醇发酵过程的精准检测,其次基于多元变量分析,建立葡萄糖、乙醇和乳酸浓度变化的预测模型,实现对发酵过程中各成分浓度变化的准确有效分析。【结论】成功建立了一种评价资源微生物尤其是工业菌株发酵液多种组分的拉曼光谱分析方法。该方法为运动发酵单胞菌等工业菌株利用多组分底物工业化生产不同产物的实时检测,以及其他微生物尤其工业菌株的选育和过程优化提供了新方法。     

Formation and Fate of Fermentation Products in Hot Spring Cyanobacterial Mats

The fate of representative fermentation products (acetate, propionate, butyrate, lactate, and ethanol) in hot spring cyanobacterial mats was investigated. The major fate during incubations in the light was photoassimilation by filamentous bacteria resembling Chloroflexus aurantiacus. Some metabolism of all compounds occurred under dark aerobic conditions. Under dark anaerobic conditions, only lactate was oxidized extensively to carbon dioxide. Extended preincubation under dark anaerobic conditions did not enhance anaerobic catabolism of acetate, propionate, or ethanol. Acetogenesis of butyrate was suggested by the hydrogen sensitivity of butyrate conversion to acetate and by the enrichment of butyrate-degrading acetogenic bacteria. Accumulation of fermentation products which were not catabolized under dark anaerobic conditions revealed their importance. Acetate and propionate were the major fermentation products which accumulated in samples collected at temperatures ranging from 50 to 70°C. Other organic acids and alcohols accumulated to a much lesser extent. Fermentation occurred mainly in the top 4 mm of the mat. Exposure to light decreased the accumulation of acetate and presumably of other fermentation products. The importance of interspecies hydrogen transfer was investigated by comparing fermentation product accumulation at a 65°C site, with naturally high hydrogen levels, and a 55°C site, where active methanogenesis prevented significant hydrogen accumulation. There was a greater relative accumulation of reduced products, notably ethanol, in the 65°C mat.     

生防链霉菌ZM-16的发酵产物生物活性及其微波诱变育种

【目的】链霉菌ZM-16对多种细菌有良好的抑菌作用,其发酵产物的主要活性物质为放线菌素D。本研究旨在进一步探讨其抗真菌活性,并通过诱变育种的方法对菌种进行改良,以提高活性物质的产量,从而为其在植物病害生物防治领域的实践应用奠定基础。【方法】利用液体发酵的方法获取活性产物并对其进行粗提取;利用抑菌圈法检测菌株发酵产物对11种植物病原真菌的抑制作用;通过微波处理并利用抗生素抗性筛选的方法对菌株进行诱变育种。【结果】粗提液对11种植物病原真菌均具有抑菌效果,最为明显的3种病菌分别是苹果炭疽病菌、油菜菌核病菌和禾谷镰刀病菌;经微波诱变筛选到了一株耐利福平突变株,其放线菌素D的产量提高了36.75%;传代研究表明其经过10代选育,遗传稳定性较好。【结论】链霉菌ZM-16的发酵产物具有良好的抗植物病原真菌的活性,经过育种后其活性产物产量也有所提高,因此具有较高的实际应用价值。     

Lactic-acid fermentation as a low-cost means of food preservation in tropical countries

Abstract The range of traditional lactic-acid-fermented foods in tropical countries is briefly reviewed. Recent studies on the lactic acid fermentation of fish and cassava products are described. Lactic-acid-fermented fish products may offer considerable scope for the development of new food products and for the use of under-utilised fish species. Lactic-acid-fermented fish products are common in parts of Asia; methods to improve the product and shelf-life quality, to reduce microbial risks and to accelerate the process are described. This work is based on fish/salt/carbohydrate model systems. The nutritional aspects of cassava fermentation are discussed with respect to factors involved in determining residual cyanide levels; the possible anti-nutritional rôle of condensed tannins is mentioned. The increasing consumption of meat products in tropical countries emphasises the need for a preservation method that does not depend on refrigeration. The possible production of sausage ingredients preserved by lactic acid fermentation, and the associated research needs are described.     

Solid-state (solid-substrate) food/beverage fermentations involving fungi

“Solid-substrate” fermentation developed in the Orient is a very useful fermentation method. It is presently used to produce a variety of foods, beverages and related products. Solid-substrate fermentation products utilizing fungi including soy sauce, miso and tempe, ontjom, sake, and bread have been produced for centuries at the home and village level. They are examples of economical methods of preserving and improving the flavor, texture and nutritive values of cereal/legume substrates. “Solid-substrate” fermentation is also applied to animal products such as milk to produce Roquefort and Camembert cheeses which diversify the food flavors available to man “Solid-substrate”fermentation has certain advantages. The substrate is concentrated; the product can be extracted with relatively small quantities of solvent; the product can be easily dehydrated; moisture level can be controlled favoring the desired organisms; enzyme concentration is generally higher than is submerged fermentation; product concentration is generally higher than in submerged cultures; it is the only technique that yields true mushroom fruiting bodies and it can be used not only for production of crude enzyme concentrates (koji) but also for raising the protein content of high starch substrates. It also can be used to increase the content of vitamins at low cost. Disadvantages of “solid-substrates”from the modern industrial processing view point are the greater difficulty of handling solid substrate and the greater difficulty of controlling the fermentation parameters, temperature, pH and oxygen, and rate of microbial growth compared with liquid submerged fermentations.     

By-product inhibition effects on ethanolic fermentation by Saccharomyces cerevisiae

Inhibition by secondary fermentation products may limit the ultimate productivity of new glucose to ethanol fermentation processes. New processes are under development whereby ethanol is selectively removed from the fermenting broth to eliminate ethanol inhibition effects. These processes can concentrate minor secondary products to the point where they become toxic to the yeast. Vacuum fermentation selectively concentrates nonvolatile products in the fermentation broth. Membrane fermentation systems may concentrate large molecules which are sterically blocked from membrane transport. Extractive fermentation systems, employing nonpolar solvents, may concentrate small organic acids. By-product production rates and inhibition levels in continuous fermentation with Saccharomyces cerevisiae have been determined for acetaldehyde, glycerol, formic, lactic, and acetic acids, 1-propanol, 2-methyl-1-butanol, and 2,3-butanediol to assess the potential effects of these by-products on new fermentation processes. Mechanisms are proposed for the various inhibition effects observed.     

The fermentation pathways of Escherichia coli

Abstract Under anaerobic conditions and in the absence of alternative electron acceptors Escherichia coli converts sugars to a mixture of products by fermentation. The major soluble products are acetate, ethanol, lactate and formate with smaller amounts of succinate. In addition the gaseous products hydrogen and carbon dioxide are produced in substantial amounts. The pathway generating fermentation products is branched and the flow down each branch is varied in response both the pH of the culture medium and the nature of the fermentation substrate. In particular, the ratio of the various fermentation products is manipulated in order to balance the number of reducing equivalents generated during glycolytic breakdown of the substrate. The enzymes and corresponding genes involved in these fermentation pathways are described. The regulatory responses of these genes and enzymes are known but the details of the underlying regulatory mechanisms are still obscure.     

The fermentation pathways of Escherichia coli

Under anaerobic conditions and in the absence of alternative electron acceptors Escherichia coli converts sugars to a mixture of products by fermentation. The major soluble products are acetate, ethanol, acetate and formate with smaller amounts of succinate. In addition the gaseous products hydrogen and carbon dioxide are produced in substantial amounts. The pathway generating fermentation products is branched and the flow down each branch is varied in response both to the pH of the culture medium and the nature of the fermentation substrate. In particular, the ratio of the various fermentation products is manipulated in order to balance the number of reducing equivalents generated during glycolytic breakdown of the substrate. The enzymes and corresponding genes involved in these fermentation pathways are described. The regulatory responses of these genes and enzymes are known but the details of the underlying regulatory mechanisms are still obscure.     

In-situ recovery of butanol during fermentation

End product inhibition can be reduced by the in situ removal of inhibitory fermentation products as they form. Extractive fermentation, in which an immiscible organic solvent is added to the fermentor in order to extract inhibitory products, was applied to the acetone-butanol fermentation. Six solvents or solvent mixtures were tested in batch extractive fermentations: kerosene, 30 wt% tetradecanol in kerosene, 50 wt% dodecanol in kerosene, oleyl alcohol, 50 wt% oleyl alcohol in a decane fraction and 50 wt% oleyl alcohol in benzyl benzoate. The best results were obtained with oleyl alcohol or a mixture of oleyl alcohol and benzyl benzoate. In normal batch fermentation of Clostridium acetobutylicum, glucose consumption is limited to about 80 kg/m³ due to the accumulation of butanol in the broth. In extractive fermentation using oleyl alcohol or a mixture of oleyl alcohol and benzyl benzoate, over 100 kg/m³ of glucose can be fermented. Removal of butanol from the broth as it formed also increased the rate of butanol production. Maximum volumetric butanol productivity was increased by as much as 60% in extractive fermentation compared to batch fermentation. Butanol productivities obtained in extractive fermentation compare favorably with other in situ product removal fermentations.