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.     

Bacteriocins from lactic acid bacteria: production, purification, and food applications

In fermented foods, lactic acid bacteria (LAB) display numerous antimicrobial activities. This is mainly due to the production of organic acids, but also of other compounds, such as bacteriocins and antifungal peptides. Several bacteriocins with industrial potential have been purified and characterized. The kinetics of bacteriocin production by LAB in relation to process factors have been studied in detail through mathematical modeling and positive predictive microbiology. Application of bacteriocin-producing starter cultures in sourdough (to increase competitiveness), in fermented sausage (anti-listerial effect), and in cheese (anti-listerial and anti-clostridial effects), have been studied during in vitro laboratory fermentations as well as on pilot-scale level. The highly promising results of these studies underline the important role that functional, bacteriocinogenic LAB strains may play in the food industry as starter cultures, co-cultures, or bioprotective cultures, to improve food quality and safety. In addition, antimicrobial production by probiotic LAB might play a role during in vivo interactions occurring in the human gastrointestinal tract, hence contributing to gut health.     

Functional and safety aspects of enterococci in dairy foods

The genus Enterococcus like other LAB has also been featured in dairy industry for decades due to its specific biochemical traits such as lipolysis, proteolysis, and citrate breakdown, hence contributing typical taste and flavor to the dairy foods. Furthermore, the production of bacteriocins by enterococci (enterocins) is well documented. These technological applications have led to propose enterococci as adjunct starters or protective cultures in fermented foods. Moreover, enterococci are nowadays promoted as probiotics, which are claimed for the maintenance of normal intestinal microflora, stimulation of the immune system and improvement of nutritional value of foods. At the same time, enterococci present an emerging pool of opportunistic pathogens for humans as they cause disease, possess agents for antibiotic resistance, and are frequently armed with potential virulence factors. Because of this “dualistic” nature, the use of enterococci remains a debatable issue. However, based on a long history of safe association of particular enterococci with some traditional food fermentations, the use of such strains appears to bear no particular risk for human health. Abundance of knowledge as well as progress in molecular techniques has, however, enabled exact characterization and safety assessment of strains. Therefore, a balanced evaluation of both, beneficial and undesirable nature of enterococci is required. A clear understanding of their status may, therefore, allow their safe use as a starter, or a probiotic strain. The present review describes the broader insight of the benefits and risks of enterococci in dairy foods and their safety assessment.     

Microencapsulation in food science and biotechnology

Microencapsulation can represent an excellent example of microtechnologies applied to food science and biotechnology. Microencapsulation can be successfully applied to entrap natural compounds, like essential oils or vegetal extracts containing polyphenols with well known antimicrobial properties to be used in food packaging. Microencapsulation preserves lactic acid bacteria, both starters and probiotics, in food and during the passage through the gastrointestinal tract, and may contribute to the development of new functional foods.     

Biotechnology in the Production and Modification of Biopolymers for Foods

Abstract

Long-chain, high-molecular-weight polymers that dissolve or disperse in water to give thickening and sometimes gelling and/or emulsifying effects are indispensable tools in food product formulation. Most of these polymers are polysaccharides, and their functional properties in foods are determined by quite subtle structural characteristics. Biotechnology offers the means for the modification of biopolymer structure to achieve desirable changes in functional properties. In this article, the impact of recent advances in traditional biotechnology (fermentation and enzymology), as well as in the newer sciences of molecular biology (genetic manipulation and protein engineering), on the development of food biopolymers is critically assessed.     

Tapé Fermentation

Microorganisms isolated from ragi, originally obtained from Indonesia, were selected for their ability to convert steamed glutinous rice into tapé, an Indonesian fermented food. A mixture of Chlamydomucor oryzae and Endomycopsis fibuliger had good fermentation characteristics. Prepared starters, produced by growing pure cultures on rice and drying them, were as active as pure cultures grown for 4 days on Difco mycological agar slants at 30 C.     

Short-chain fatty acid and vitamin production potentials of Lactobacillus isolated from fermented foods of Khasi Tribes,Meghalaya, India

Vitamins and SCFA (short-chain fatty acids) production from Lactobacillus isolates are studied due to its health benefits to the human hosts. Lactobacillus strains are widely used in fermented foods, and few of them are reported with vitamin and SCFA production potential. Therefore, in the present study, vitamins and SCFA production capability of isolates were studied to find the potent Lactobacillus cultures for value-added functional food product development. Five Lactobacillus strains, i.e., KGL2, KGL3A, KGL4, RNS4, and WTS4, were isolated from rice-based traditional fermented foods of Garo Hills, Meghalaya, India. All the well grown isolates were morphologically, physiologically, and genetically characterized. Then, vitamins and SCFA were estimated using HPLC based methods. Vitamins produced in vitamins free assay medium and SCFA in milk medium are produced by Lactobacillus. Lactic acid bacteria produce essential vitamins like riboflavin, folate, cobalamin, and SCFA which have health impacts (anti-obesity, anti-diabetics, anti-microbial, and other chronic diseases prevention) to the host. These vitamins are essential for cellular and metabolic growth of living system. In the study, five potent Lactobacillus isolates viz., KGL2 (Lactobacillus fermentum), KGL3A (Lactobacillus plantarum), KGL4 (Lactobacillus fermentum), RNS4 (Lactobacillus rhamnosus), and WTS4 (Lactobacillus fermentum) were considered for vitamins (B2, B12, and B9) and SCFA productions (lactate, butyrate, and acetate). However, KGL3A had shown highest B2 production (0.7 μg/ml) while KGL2 exhibited maximum B12 production (0.05 μg/ml) after 36 h. Moreover, WTS4 attributed highest folate production (0.09 μg/ml) after 24 h. In addition, RNS4 reported the maximum short-chain fatty acid production (0.77 g/l acetic acid, 0.26 g/l lactic acid, and 0.008 g/l butyric acid respectively). Potent Lactobacillus isolates from traditional fermented foods of Garo Hills, Meghalaya, India (North East Part of India) showed maximum production of B2, B9, and B12 as well as short-chain fatty acids and could be used for their application as health beneficial functional fermented dairy products.     

Tapé fermentation

Microorganisms isolated from ragi, originally obtained from Indonesia, were selected for their ability to convert steamed glutinous rice into tapé, an Indonesian fermented food. A mixture of Chlamydomucor oryzae and Endomycopsis fibuliger had good fermentation characteristics. Prepared starters, produced by growing pure cultures on rice and drying them, were as active as pure cultures grown for 4 days on Difco mycological agar slants at 30 C.     

Microbial transglutaminase—a review of its production and application in food processing

Transglutaminase (EC 2.3.2.13) catalyses an acyl-transfer reaction in which the -carboxamide groups of peptide-bound glutaminyl residues are the acyl donors. The enzyme catalyses in vitro cross-linking in whey proteins, soya proteins, wheat proteins, beef myosin, casein and crude actomysin refined from mechanically deboned poultry meat. In recent years, on the basis of the enzyme's reaction to gelatinize various food proteins through the formation of cross-links, this enzyme has been used in attempts to improve the functional properties of foods. Up to now, commercial transglutaminase has been merely obtained from animal tissues. The complicated separation and purification procedure results in an extremely high price for the enzyme, which hampers a wide application in food processing. Recently studies on the production of transglutaminase by microorganisms have been started. The enzyme obtained from microbial fermentation has been applied in the treatment of food of different origins. Food treated with microbial transglutaminase appeared to have an improved flavour, appearance and texture. In addition, this enzyme can increase shelf-life and reduce allergenicity of certain foods. This paper gives an overview of the development of microbial transglutaminase production, including fermentation and down-stream processing, as well as examples of how to use this valuable enzyme in processing foods of meat, fish and plant origin.     

The art of strain improvement of industrial lactic acid bacteria without the use of recombinant DNA technology

The food industry is constantly striving to develop new products to fulfil the ever changing demands of consumers and the strict requirements of regulatory agencies. For foods based on microbial fermentation, this pushes the boundaries of microbial performance and requires the constant development of new starter cultures with novel properties. Since the use of ingredients in the food industry is tightly regulated and under close scrutiny by consumers, the use of recombinant DNA technology to improve microbial performance is currently not an option. As a result, the focus for improving strains for microbial fermentation is on classical strain improvement methods. Here we review the use of these techniques to improve the functionality of lactic acid bacteria starter cultures for application in industrial-scale food production. Methods will be described for improving the bacteriophage resistance of specific strains, improving their texture forming ability, increasing their tolerance to stress and modulating both the amount and identity of acids produced during fermentation. In addition, approaches to eliminating undesirable properties will be described. Techniques include random mutagenesis, directed evolution and dominant selection schemes.     

Functional relevance and health benefits of soymilk fermented by lactic acid bacteria

The growing interest of consumers towards nutritionally enriched, and health promoting foods, provoke interest in the eventual development of fermented functional foods. Soymilk is a growing trend that can serve as a low-cost non-dairy alternative with improved functional and nutritional properties. Soymilk acts as a good nutrition media for the growth and proliferation of the micro-organism as well as for their bioactivities. The bioactive compounds produced by fermentation of soymilk with lactic acid bacteria (LAB) exhibit enhanced nutritional values, and several improved health benefits including antihypertensive, antioxidant, antidiabetic, anticancer and hypocholesterolaemic effects. The fermented soymilk is acquiring a significant position in the functional food industry due to its increased techno-functional qualities as well as ensuring the survivability of probiotic bacteria producing diverse metabolites. This review covers the important benefits conferred by the consumption of soymilk fermented by LAB producing bioactive compounds. It provides a holistic approach to obtain existing knowledge on the biofunctional attributes of fermented soymilk, with a focus on the functionality of soymilk fermented by LAB.     

Putting microbes to work: dairy fermentation, cell factories and bioactive peptides. Part I: overview

A variety of milk-derived biologically active peptides have been shown to exert both functional and physiological roles in vitro and in vivo, and because of this are of particular interest for food science and nutrition applications. Biological activities associated with such peptides include immunomodulatory, antibacterial, anti-hypertensive and opioid-like properties. Milk proteins are recognized as a primary source of bioactive peptides, which can be encrypted within the amino acid sequence of dairy proteins, requiring proteolysis for release and activation. Fermentation of milk proteins using the proteolytic systems of lactic acid bacteria (LAB) is an attractive approach for generation of functional foods enriched in bioactive peptides given the low cost and positive nutritional image associated with fermented milk drinks and yoghurt. In this review, we discuss the exploitation of such fermentation towards the development of functional foods conferring specific health benefits to the consumer beyond basic nutrition. In particular, in Part I, we focus on the release of encrypted bioactive peptides from a range of food protein sources, as well as the use of LAB as cell factories for the de novo generation of bioactivities.     

Functional Foods — Lebensmittel der Zukunft?: Maßgeschneiderte Ernährung

Functional foods might be helpful in improving the nutritional status and preventing certain diseases. In order to inform the consumer about the benefit of a product it will be necessary to enable scientifically proved health claims. These health claims have to be supported by studies and should make clear how a product can influence health. Only if there are proven facts, functional foods could establish on the market as foods of the future in the longer term beside the naturally healthful products. It will be of no use neither to the consumer nor to the food industry to promote these product group with exaggerated promises as a kind of miracle cure which can help against all diseases. The acceptance of the consumer will depend on credible product concepts. Another important precondition for functional foods is that there are absolutely no health risks associated with the consumption of these products. Recommendations regarding fortification and intake of functional foods must consider this aspect. Side effects by excessive doses or imbalances are to be avoided. The consumer should know that the point is not to take as much as possible of potentially healthful single substances but to show clearly that physiological dosages, which can also be attained by a higher intake of traditional food are associated with the best benefit‐risk relation, i.e. show the greatest benefit and minimal risk. In general functional foods do not resolve any nutritional problem. The effects are limited, especially if the nutrition is imbalanced (e.g. hyperenergetic, high fat). In these cases the addition of functional foods offers no or only small corrective effects. Functional foods represent no substitute for a fully balanced nourishment with a high amount of naturally healthy foods such as vegetables, fruits, whole grain products as well as milk and milk products.     

传统与未来的碰撞：食品发酵工程技术与应用进展

随着生物技术的飞速发展,作为食品生物工程的主要组成部分,食品发酵工程技术不断升级,在传统发酵食品的菌种、发酵过程、产品品质得到改善的同时,生物制造的功能食品组分、未来食品等新型产品也应运而生。首先概述了由生物技术和信息技术的进步带来的食品发酵研究手段与生产方式的多层面变革,并重点阐释了利用食品合成生物学设计构建细胞工厂的思路和方法,以及食品生物工程在微生物分析、过程工程和分离工程方面的智能化进程。其次,介绍了现代食品生物工程技术在改善传统发酵食品品质及安全性、生产功能食品组分、添加剂和酶制剂、创制未来食品和开发新型益生食品方面的应用进展。最后,对全球和我国食品发酵产业面临的挑战和未来发展趋势进行了总结和展望,以期为食品发酵的技术革新和工业化应用提供参考。     

Use of lacticin 481 to facilitate delivery of the bacteriophage resistance plasmid, pCBG104 to cheese starters

AIMS: Use of lacticin 481 to facilitate the conjugal transfer of the bacteriophage resistance plasmid pCBG104 to various starter cultures. METHODS AND RESULTS: A raw milk isolate of Lactococcus was found to harbour determinants for lacticin 481 production and immunity and phage resistance on a plasmid designated pCBG104. The lacticin 481 was successfully used to mobilize the phage resistance determinant to a variety of cheese starters enabling the formation of highly phage resistant starters. In addition, it facilitated the stacking of a number of phage resistance genes, namely a type I restriction modification system, a phage abortive infection system and a phage adsorption blocking system in a single Lactococcus strain without the use of recombinant techniques. The transconjugants were all shown to produce lacticin 481 and to contain the entire 481 operon. Subsequently one transconjugant was selected and successfully used for large-scale cheddar cheese manufacture. CONCLUSIONS: Lacticin 481 could be used as a food-grade selectable marker to facilitate the introduction of advantageous traits to starter cultures for industrial food fermentations. SIGNIFICANCE AND IMAPCT OF THE STUDY: Food-grade selectable markers greatly facilitate the introduction of various advantageous traits to starter cultures for industrial food fermentation. Indeed self-cloning which is becoming increasingly important for strain improvement has a requirement for the identification and demonstration of the utility of tools such as lacticin 481.     

An introduction to rod-shaped lactic-acid bacteria

The genus Lactobacillus is mainly found in the intestinal tract of healthy humans and animals as well as in fermenting vegetables or plant materials, such as silage. It has a moderate diffusion in meat products and is rarely found in wines and beers. On the other hand, rod-shaped lactic-acid bacteria are largely used in the preparation of a variety of foods and feed products. As starter cultures, they are omnipresent in cheeses and dairy manufacturing. Specific fermentation processes have been developed in order to encourage the growth of the desired species, some of which are fastidious organisms such as L. delbrueckii ssp. bulgaricus, L. helveticus and L. sanfrancisco. In addition, a promising and interesting perspective is the use of rod-shaped lactic-acid bacteria, primarily L. acidophilus, L. reuteri and L. salivarius as probiotic starters to preserve the natural biological equilibrium of the intestinal tract.     

Lactic acid bacteria producing B-group vitamins: a great potential for functional cereals products

Wheat contains various essential nutrients including the B group of vitamins. However, B group vitamins, normally present in cereals-derived products, are easily removed or destroyed during milling, food processing or cooking. Lactic acid bacteria (LAB) are widely used as starter cultures for the fermentation of a large variety of foods and can improve the safety, shelf life, nutritional value, flavor and overall quality of the fermented products. In this regard, the identification and application of strains delivering health-promoting compounds is a fascinating field. Besides their key role in food fermentations, several LAB found in the gastrointestinal tract of humans and animals are commercially used as probiotics and possess generally recognized as safe status. LAB are usually auxotrophic for several vitamins although certain strains of LAB have the capability to synthesize water-soluble vitamins such as those included in the B group. In recent years, a number of biotechnological processes have been explored to perform a more economical and sustainable vitamin production than that obtained via chemical synthesis. This review article will briefly report the current knowledge on lactic acid bacteria synthesis of vitamins B2, B11 and B12 and the potential strategies to increase B-group vitamin content in cereals-based products, where vitamins-producing LAB have been leading to the elaboration of novel fermented functional foods. In addition, the use of genetic strategies to increase vitamin production or to create novel vitamin-producing strains will be also discussed.     

Technological and molecular diversity of Lactobacillus plantarum strains isolated from naturally fermented sourdoughs

Thirty Lactobacillus (L.) plantarum strains, isolated from sourdough, were identified by biochemical tests as well as 16S rDNA sequencing and differentiated on the basis of technological properties, such as amylase, protease, phytase and antirope activities. These properties were shown to be widely differing among the strains, indicating a significant technological diversity. Genetic differentiation was achieved by restriction endonuclease analysis-pulsed field gel electrophoresis (REA-PFGE) that allowed the L. plantarum strains to be divided into 10 different genomic groups. Moreover, 32 different starters were employed in dough making experiments; each starter consisted of a single strain of L. plantarum associated with a maltose positive or a maltose negative yeast. The technological properties of the doughs were greatly influenced by the type of strain included in the starter. The time of leavening and the acidification activities detected in the dough were enhanced by the presence of L. plantarum strains. The bacterial and yeast contents and fermentation properties were statistically treated by principal component analysis (PCA), which allowed the discrimination of different typologies of dough. The study of the peculiar characteristics of different strains of L. plantarum is fundamental for a better understanding of their potential in affecting the nutritional value, quality and stability of the baked goods. L. plantarum strains are able to differentially influence the dough quality when employed as starters.     

Production of ethanol,organic acids and hydrogen: an opportunity for mixed culture biotechnology?

Anaerobic fermentation of biodegradable organic materials is usually carried out to obtain the final product, methane, a valuable energy source. However, it is also well known that various intermediates are produced in this process, e.g. ethanol, volatile organic acids and hydrogen. All these species have applications and value as fuels or chemicals. This paper shows a critical analysis of the potential of using anaerobic fermentation by mixed cultures to produce intermediates, e.g. ethanol, acetic, lactic and butyric acid and hydrogen, rather than methane. This paper discusses the current processes to produce these chemicals and compares them with the alternative approach of using open mixed cultures to produce them simultaneously via fermentation from renewable resources. None of these chemicals is currently produced via mixed culture fermentation: ethanol and lactic acid are usually produced in pure culture fermentation using food crops, e.g. corn or sugar cane, as starting materials; hydrogen, acetic and butyric acids are mainly produced via chemical synthesis from fossil fuel derived starting materials. A possible flow-sheet for the production of these chemicals from organic waste using mixed culture fermentation is proposed and the advantages and disadvantages of this process compared to current processes are critically discussed. The paper also discusses the research challenges which need to be addressed to make this process feasible.