Rheology,oxygen transfer,and molecular weight characteristics of poly(glutamic acid) fermentation by Bacillus subtilis

Poly(glutamic acid) (PGA) is a water-soluble, biodegradable biopolymer that is produced by microbial fermentation. Recent research has shown that PGA can be used in drug delivery applications for the controlled release of paclitaxel (Taxol) in cancer treatment. A fundamental understanding of the key fermentation parameters is necessary to optimize the production and molecular weight characteristics of poly(glutamic acid) by Bacillus subtilis for paclitaxel and other applications of pharmaceuticals for controlled release. Because of its high molecular weight, PGA fermentation broths exhibit non-Newtonian rheology. In this article we present experimental results on the batch fermentation kinetics of PGA production, mass transfer of oxygen, specific oxygen uptake rate, broth rheology, and molecular weight characterization of the PGA biopolymer.     

High yield and cost‐effective production of poly(γ‐glutamic acid) with Bacillus subtilis

Poly(γ‐glutamic acid) (γ‐PGA) is a promising biopolymer with many potential industrial and pharmaceutical applications. To reduce the production costs, the effects of yeast extract and L ‐glutamate in the substrate for γ‐PGA production were investigated systematically at shake flask scale. The results showed that lower concentrations of yeast extract (40 g/L) and L ‐glutamate (30 g/L) were beneficial for the cost‐effective production of γ‐PGA in the formulated medium. By maintaining the glucose concentration in the range of 3–10 g/L via a fed‐batch strategy in a 10‐L fermentor, the production of γ‐PGA was greatly improved with the highest γ‐PGA concentration of 101.1 g/L, a productivity of 2.19 g/L·h and a yield of 0.57 g/g total substrate, which is about 1.4‐ to 3.2‐fold higher than those in the batch fermentation. Finally, this high‐density fermentation process was successfully scaled up in a 100‐L fermentor. The present work provides a powerful approach to produce this biopolymer as a bulk chemical in large scale.     

Biotechnological advances on Penicillin G acylase: Pharmaceutical implications,unique expression mechanism and production strategies

In light of unrestricted use of first-generation penicillins, these antibiotics are now superseded by their semisynthetic counterparts for augmented antibiosis. Traditional penicillin chemistry involves the use of hazardous chemicals and harsh reaction conditions for the production of semisynthetic derivatives and, therefore, is being displaced by the biosynthetic platform using enzymatic transformations. Penicillin G acylase (PGA) is one of the most relevant and widely used biocatalysts for the industrial production of β-lactam semisynthetic antibiotics. Accordingly, considerable genetic and biochemical engineering strategies have been devoted towards PGA applications. This article provides a state-of-the-art review in recent biotechnological advances associated with PGA, particularly in the production technologies with an emphasis on using the Escherichia coli expression platform.     

A novel Method for the selective recovery and purification of γ‐polyglutamic acid from Bacillus licheniformis fermentation broth

Microbially produced gamma‐polyglutamic acid (γ‐PGA) is a commercially important biopolymer with many applications in biopharmaceutical, food, cosmetic and waste‐water treatment industries. Owing to its increasing demand in various industries, production of γ‐PGA is well documented in the literature, however very few methods have been reported for its recovery. In this paper, we report a novel method for the selective recovery and purification of γ‐PGA from cell‐free fermentation broth of Bacillus licheniformis. The cell‐free fermentation broth was treated with divalent copper ions, resulting in the precipitation of γ‐PGA, which was collected as a pellet by centrifugation. The pellet was resolubilized and dialyzed against de‐ionized water to obtain the purified γ‐PGA biopolymer. The efficiency and selectivity of γ‐PGA recovery was compared with ethanol precipitation method. We found that 85% of the original γ‐PGA content in the broth was recovered by copper sulfate‐induced precipitation, compared to 82% recovery by ethanol precipitation method. Since ethanol is a commonly used solvent for protein precipitation, the purity of γ‐PGA precipitate was analyzed by measuring proteins that co‐precipitated with γ‐PGA. Of the total proteins present in the broth, 48% proteins were found to be co‐precipitated with γ‐PGA by ethanol precipitation, whereas in copper sulfate‐induced precipitation, only 3% of proteins were detected in the final purified γ‐PGA, suggesting that copper sulfate‐induced precipitation offers better selectivity than ethanol precipitation method. Total metal content analysis of the purified γ‐PGA revealed the undetectable amount of copper ions, whereas other metal ions detected were in low concentration range. The purified γ‐PGA was characterized using infrared spectroscopy. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Kimchi microflora: history,current status,and perspectives for industrial kimchi production

Kimchi, a traditional Korean food made by the fermentation of vegetables, has become popular globally because of its organoleptic, beneficial, and nutritional properties. Spontaneous kimchi fermentation in unsterilized raw materials leads to the growth of various lactic acid bacteria (LAB), which results in variations in the taste and sensory qualities of kimchi products and difficulties in the standardized industrial production of kimchi. Raw materials, kimchi varieties, ingredients, and fermentation conditions have significant effects on the microbial communities and fermentative characteristics of kimchi during fermentation. Heterofermentative LAB belonging to the genera Leuconostoc, Lactobacillus, and Weissella are likely to be key players in kimchi fermentation and have been subjected to genomic and functional studies to gain a better understanding of the fermentation process and beneficial effects of kimchi. The use of starter cultures has been considered for the industrial production of high quality, standardized kimchi. Here, we review the composition and biochemistry of kimchi microflora communities, functional and genomic studies of kimchi LAB, and perspectives for industrial kimchi production.     

Rapeseed and sunflower meal: a review on biotechnology status and challenges

Rapeseed and sunflower are two of the world's major oilseeds. Rapeseed and sunflower meal (RSM and SFM), the by-products of oil extraction, are produced in large quantities. They are mainly composed of proteins, lignocellulosic fibres and minerals. They were initially used as a protein complement in animal feed rations and sometimes as fertilizer or as combustible source. More recently, new alternatives to these traditional uses have been developed that draw on the structure and physicochemical properties of RSM and SFM, which are plentiful sources of nitrogen and carbon nutrients. This feature, together with their cheapness and ready availability, supports the cultivation of various microorganisms in both submerged cultures and solid-state fermentation. Recent studies have thus emphasized the potential utilisation of RSM and SFM in fermentative processes, including saccharification and production of enzymes, antibiotics, antioxidants and other bio-products, opening new challenging perspectives in white biotechnology applications.     

Screening of phytase producers and optimization of culture conditions for submerged fermentation

Phytase (myo-inositol-hexakisphosphate phosphohydrolase) is an enzyme, which breaks down phytate to inositol and orthophosphoric acid. Phytase has been used as feed additive, and in some medical applications for years. To date, phytase production has been usually performed as a solid-state fermentation with small production volumes. Therefore, the aim of this study was to increase the phytase activity in submerged fermentations by screening several microorganism strains based on the literature to select the most productive phytase producer and optimizing growth parameters such as temperature, pH, and aeration level using response surface methodology (RSM). As a result, among the four different microorganisms evaluated, Aspergillus ficuum (NRRL 3135) was selected as the most productive strain. Optimum temperature, pH, and aeration values were determined as 33 °C, 4.5, and 0.9 vvm, respectively, for A. ficuum in 2-l batch submerged phytase productions. Under these conditions, phytase activity was measured as 2.27 U/ml. Therefore, this is a unique study showing the production of phytase with A. ficuum successfully in submerged fermentation as opposed to the traditional solid-state fermentation.     

Amino acids production focusing on fermentation technologies – A review

Amino acids are attractive and promising biochemicals with market capacity requirements constantly increasing. Their applicability ranges from animal feed additives, flavour enhancers and ingredients in cosmetic to specialty nutrients in pharmaceutical and medical fields.This review gives an overview of the processes applied for amino acids production and points out the main advantages and disadvantages of each.Due to the advances made in the genetic engineering techniques, the biotechnological processes, and in particular the fermentation with the aid of strains such as Corynebacterium glutamicum or Escherichia coli, play a significant role in the industrial production of amino acids. Despite the numerous advantages of the fermentative amino acids production, the process still needs significant improvements leading to increased productivity and reduction of the production costs.Although the production processes of amino acids have been extensively investigated in previous studies, a comprehensive overview of the developments in bioprocess technology has not been reported yet. This review states the importance of the fermentation process for industrial amino acids production, underlining the strengths and the weaknesses of the process. Moreover, the potential of innovative approaches utilizing macro and microalgae or bacteria are presented.     

Oil cakes and their biotechnological applications--a review

Oil cakes have been in use for feed applications to poultry, fish and swine industry. Being rich in protein, some of these have also been considered ideal for food supplementation. However, with increasing emphasis on cost reduction of industrial processes and value addition to agro-industrial residues, oil cakes could be ideal source of proteinaceous nutrients and as support matrix for various biotechnological processes. Several oil cakes, in particular edible oil cakes offer potential benefits when utilized as substrate for bioprocesses. These have been utilized for fermentative production of enzymes, antibiotics, mushrooms, etc. Biotechnological applications of oil cakes also include their usages for vitamins and antioxidants production. This review discusses various applications of oil cakes in fermentation and biotechnological processes, their value addition by implementation in feed and energy source (for the production of biogas, bio-oil) as well.     

Cyclosporin A--a review on fermentative production, downstream processing and pharmacological applications

In present times, the immunosuppressants have gained considerable importance in the world market. Cyclosporin A (CyA) is a cyclic undecapeptide with a variety of biological activities including immunosuppressive, anti-inflammatory, antifungal and antiparasitic properties. CyA is produced by various types of fermentation techniques using Tolypocladium inflatum. In the present review, we discuss the biosynthetic pathway, fermentative production, downstream processing and pharmacological activities of CyA.     

Comparative study of protease production in solid substrate fermentation versus submerged fermentation

Attempts have been made to compare solid substrate fermentation (SSF) with submerged fermentation for the production of proteases by Bacillus amyloliquefaciens. In submerged fermentation it produced 800,000 units of enzyme under optimal conditions in a 20-litre fermentor whereas in solid substrate, it produced 250,000 units/g. Owing to the simplicity and easiness of operation of SSF and for applications like unhairing, biodetergents and bating the former would be advantageous for the production of proteases.     

New approaches for itaconic acid production: bottlenecks and possible remedies

Currently, growing attention is being devoted to the conversion of biomass into value-added products, such as itaconic acid (IA), which is considered as the cleanest alternative to petroleum-based acrylic acid. IA is an unsaturated dicarboxylic acid that is used as a building block chemical for the production of several value-added products such as poly-itaconic acid. IA and its derivatives have a wide range of potential applications in textile, paint, pharmaceutical and chemical industries. Presently, industries are producing IA on the large scale by fermentation from glucose. However, due to the primary utility of glucose as a food, it cannot meet the global demand for IA production in an economical way. The main challenge, so far, has been the production technology, which does not support cost-effective and competitive production of IA. This review discusses the various bottlenecks faced during each step of IA production, along with possible remedies to deal with these problems. Furthermore, it reviews the recent progress in fermentative IA production and sheds light on different microorganisms used, potential substrates and fermentation conditions. The review also covers market potential for IA, which indicates that IA can be produced cost-effectively from sustainable substrates, and it has the potential to replace petrochemicals in the near future.     

Production of bioactive metabolites by submerged fermentation of the medicinal mushroom Antrodia cinnamomea: recent advances and future development

Edible and medicinal mushrooms have usually been considered as a sustainable source of unique bioactive metabolites, which are valued as promising provisions for human health. Antrodia cinnamomea is a unique edible and medicinal fungus widespread in Taiwan, which has attracted much attention in recent years for its high value in both scientific research and commercial applications owing to its potent therapeutic effects, especially for its hepatic protection and anticancer activity. Due to the scarcity of the fruiting bodies, the cultivation of A. cinnamomea by submerged fermentation appears to be a promising substitute which possesses some unique advantages, such as short culture time period and its high feasibility for scale-up production. However, the amount of fungal bioactive metabolites derived from the cultured mycelia of A. cinnamomea grown by submerged fermentation is much less than those obtained from the wild fruiting bodies. Hence, there is an urgent need to bridge such a discrepancy on bioactive metabolites between the wild fruiting bodies and the cultured mycelia. The objective of this article is to review recent advances and the future development of the mycelial submerged fermentation of A. cinnamomea in terms of enhancement for the production of fungal bioactive components by the optimization of culture conditions and the regulation of fungal metabolism. This review provides valuable information for further biotechnological applications of A. cinnamomea as well as other mushrooms being the source of bioactive ingredients by submerged fermentation.     

Mucor indicus: Biology and industrial application perspectives: A review

Mucor indicus, one of the most important strains of zygomycetes fungi, has been the subject of several studies since a couple of hundred years ago. This fungus, regarded as a non-pathogenic dimorphic microorganism, is used for production of several beers and foods. Morphology of the fungus can be manipulated and well controlled by changing a number of parameters. Furthermore, M. indicus can grow on a variety of substrates including lignocellulosic hydrolysates which are mixtures of hexoses, pentoses, and different severe fermentation inhibitors. Indeed, high yield ethanol production is among the most important features of this strain. Presence of considerable amounts of chitosan in the cell wall is another important aspect of the fungus. Besides production of ethanol and chitosan, the biomass of this fungus has shown a great potential to be used as a rich nutritional source, e.g. fish feed. The fungus is also among the oleaginous fungi and produces high amounts of polyunsaturated fatty acids particularly γ-linolenic acid. Furthermore, the biomass autolysate has a high potential for yeast extract replacement in fermentation by the fungus. Additionally, the strain has shown promising results in heavy metal removal from wastewaters. This review discusses different aspects of biology and industrial application perspectives of M. indicus. Furthermore, open areas for the future basic and applied levels of research are also presented.     

Production of kojic acid by Aspergillus species: Trends and applications

Kojic acid (KA), produced mainly by Aspergillus species, is a product of fungal secondary metabolism and has great potential in biotechnological applications. The use of KA has steadily increased, chiefly in the pharmaceutical industry, where KA is used for skin lightning. The market for KA has grown considerably in recent years and is expected to reach $39 million by 2026. In this review, we summarise the relevant information regarding the application of KA, describe the optimal cultivation conditions for Aspergillus species used in the production of KA, and assess the prospects for the KA market. Based on our findings, we established that the highest yields of KA can be achieved using submerged fermentation with glucose and yeast extract as the primary sources of carbon and nitrogen, respectively. Furthermore, according to literature, the main species/strains reported as the best producers of KA are Aspergillus flavus (44-L), Aspergillus oryzae (AR-47 and NRRL 484), and Aspergillus terreus (C5-10 mutant of the strain PTCC 5283). Given the commercial importance of KA and the growing demand for this natural product, further studies are needed to identify novel strains of Aspergillus as potential high producers of this acid. Similarly, it will be desirable to identify novel sources of substrate for the low-cost production of KA, thereby promoting its production for use in pharmaceutical, healthcare, and other potential industrial applications. In addition, given the current limited knowledge regarding the biosynthetic pathway of KA, further studies are required to elucidate that biosynthetic pathway.     

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.     

半纤维素水解物生物转化生产木糖醇

木糖醇在食品、医药及化工行业中有着广泛的用途而深受关注。但是,传统的化学法生产木糖醇需要一系列复杂的分离纯化步骤,过高的生产成本限制了木糖醇的使用范围。发酵工艺生产木糖醇无需木糖的纯化步骤,是取代化学合成法的一条可行工艺路线。本文着重介绍产木糖醇的微生物,酵母对木糖的同化途径,半纤维素水解物的脱毒方法,影响木糖醇发酵的工艺条件等。     

Biotechnological production of ethanol from renewable resources by Neurospora crassa: an alternative to conventional yeast fermentations?

Microbial production of ethanol might be a potential route to replace oil and chemical feedstocks. Bioethanol is by far the most common biofuel in use worldwide. Lignocellulosic biomass is the most promising renewable resource for fuel bioethanol production. Bioconversion of lignocellulosics to ethanol consists of four major unit operations: pretreatment, hydrolysis, fermentation, and product separation/distillation. Conventional bioethanol processes for lignocellulosics apply commercial fungal cellulase enzymes for biomass hydrolysis, followed by yeast fermentation of resulting glucose to ethanol. The fungus Neurospora crassa has been used extensively for genetic, biochemical, and molecular studies as a model organism. However, the strain's potential in biotechnological applications has not been widely investigated and discussed. The fungus N. crassa has the ability to synthesize and secrete all three enzyme types involved in cellulose hydrolysis as well as various enzymes for hemicellulose degradation. In addition, N. crassa has been reported to convert to ethanol hexose and pentose sugars, cellulose polymers, and agro-industrial residues. The combination of these characteristics makes N. crassa a promising alternative candidate for biotechnological production of ethanol from renewable resources. This review consists of an overview of the ethanol process from lignocellulosic biomass, followed by cellulases and hemicellulases production, ethanol fermentations of sugars and lignocellulosics, and industrial application potential of N. crassa.     

Bio-hydrogen production by biodiesel-derived crude glycerol bioconversion: a techno-economic evaluation

Global biodiesel production is continuously increasing and it is proportionally accompanied by a huge amount of crude glycerol (CG) as by-product. Due to its crude nature, CG has very less commercial interest; although its pure counterpart has different industrial applications. Alternatively, CG is a very good carbon source and can be used as a feedstock for fermentative hydrogen production. Further, a move of this kind has dual benefits, namely it offers a sustainable method for disposal of biodiesel manufacturing waste as well as produces biofuels and contributes in greenhouse gas (GHG) reduction. Two-stage fermentation, comprising dark and photo-fermentation is one of the most promising options available for bio-hydrogen production. In the present study, techno-economic feasibility of such a two-stage process has been evaluated. The analysis has been made based on the recent advances in fermentative hydrogen production using CG as a feedstock. The study has been carried out with special reference to North American biodiesel market; and more specifically, data available for Canadian province, Québec City have been used. Based on our techno-economic analysis, higher production cost was found to be the major bottleneck in commercial production of fermentative hydrogen. However, certain achievable alternative options for reduction of process cost have been identified. Further, the process was found to be capable in reducing GHG emissions. Bioconversion of 1 kg of crude glycerol (70 % w/v) was found to reduce 7.66 kg CO₂ eq (equivalent) GHG emission, and the process also offers additional environmental benefits.     

Fermentative butanol production by Clostridia

Butanol is an aliphatic saturated alcohol having the molecular formula of C(4)H(9)OH. Butanol can be used as an intermediate in chemical synthesis and as a solvent for a wide variety of chemical and textile industry applications. Moreover, butanol has been considered as a potential fuel or fuel additive. Biological production of butanol (with acetone and ethanol) was one of the largest industrial fermentation processes early in the 20th century. However, fermentative production of butanol had lost its competitiveness by 1960s due to increasing substrate costs and the advent of more efficient petrochemical processes. Recently, increasing demand for the use of renewable resources as feedstock for the production of chemicals combined with advances in biotechnology through omics, systems biology, metabolic engineering and innovative process developments is generating a renewed interest in fermentative butanol production. This article reviews biotechnological production of butanol by clostridia and some relevant fermentation and downstream processes. The strategies for strain improvement by metabolic engineering and further requirements to make fermentative butanol production a successful industrial process are also discussed.