Physical and nutritional conditions for optimized production of bacteriocins by lactic acid bacteria – A review

ABSTRACT

There has been an increasing debate about the use of synthetic chemical compounds and the consequences of their use in food preservation. In this context, the utilization of some natural compounds produced by bacteria, showing an inhibitory effect against microorganisms associated with food contamination, have gained attention as preservation technology. In order to improve the production and yield costs of bacteriocins, detailed studies are necessary to determine the conditions that allow an optimized production and extraction of bacteriocins from lactic acid bacteria (LAB). In this context, this article aims to discuss the information regarding the main factors that influence bacteriocin production by LAB. The biosynthesis of bacteriocins can be influenced by various culture conditions, such as the composition of the medium, pH, temperature and growth kinetics of the microorganisms. One of the limiting factors for the use of bacteriocins on a large scale in food preservation is the economic factor. In order for the production costs of bacteriocins to be reduced, making them attractive, it is necessary to know the optimum parameters of production, thus maximizing productivity and making costs more attractive.     

Bacteriocins of lactic acid bacteria: Their potentials as food biopreservative

Abstract

Numerous strains of lactic acid bacteria used in the fermentation of foods are known to produce bacteriocins. In general, bacteriocins are a group of proteinaceous antimicrobial substances that inhibit the growth of closely related bacteria. However, some bacteriocins produced by lactic acid bacteria (LAB) exhibit a relatively broad antimicrobial spectrum and are active against several food‐spoilage and health‐threatening microorganisms. Many investigators have reported on the use of bacteriocins as food preservative to extend the shelflife of various foods. This review decribes the research that has been conducted on bacteriocinogenic lactic acid bacteria— isolated from a wide variety of foods and in some instances of animal origin—and the characteristics of bacteriocins. Special emphasis is placed on their potentials for use as food preservative and on their physicochemical nature, antibacterial spectrum, and genetic behavior.     

Development of Wide-Spectrum Hybrid Bacteriocins for Food Biopreservation

The food industry demands new procedures and methods to produce minimally processed, ready to eat food with intact nutritional, taste, and flavor properties. The biopreservation and the use of both bacteriocins produced by lactic acid bacteria (LAB) and bacteriocinogenic strains as an alternative to substitute chemical antimicrobial for food preservation became increasingly important in the last two decades. When the new proposed natural preservatives techniques are applied, probiotics food can be obtained and, simultaneously, foodborne pathogens and spoilage contaminants can diminish. However, bacteriocins produced by LAB have a narrow antibacterial spectrum and are inactive against Gram-negative bacteria like Salmonella and the emergent enterohemorrhagic Escherichia coli. Knowing the mechanism of action and the structural features of microcins synthesized by Gram-negative bacteria and with potent antimicrobial activity against the mentioned microorganism, the proposal is to obtain hybrid peptides (microcin–bacteriocin) with broad antimicrobial spectrum. This review explains how the inability of bacteriocins to cross the outer membrane of Gram-negative bacteria unable them to act on the bacteria. It will also be discussed how a hybrid bacteriocin can be obtained.     

Application of bacteriocins in vegetable food biopreservation

Bacteriocins are generally recognized as "natural" compounds able to influence the safety and quality of foods. In the past years, a lot of works have been aimed to the detection, purification and characterisation of bacteriocins, as well as to their use in food preservation strategies. A list of review articles dealing with the application of bacteriocins to the protection of foods of animal origin is also available in literature, but it lacks for a summary on the utilization of bacteriocins in vegetable foods. These biopreservatives can be used in a number of ways in food systems and this paper mainly focuses on the state-of-the-art application of bacteriocins from lactic acid bacteria (LAB) to promote the microbial stability of both fermented and non-fermented vegetable food products using bacteriocinogenic strains as starter cultures, protective cultures or co-cultures and the employment of pure bacteriocins as food additives. In addition, applications of bacteriocins from non-LAB are also reviewed. The scopes of future directions of research are summarised.     

FUNDAMENTALS AND PERSPECTIVES FOR THE USE OF BACTERIOCINS PRODUCED BY LACTIC ACID BACTERIA IN MEAT PRODUCTS

Bacteriocins of lactic acid bacteria (LAB) are proteinaceous compounds that may present antimicrobial activity towards important foodborne pathogens and spoilage-related microflora. Due to these properties, bacteriocin-producing strains or purified bacteriocins have a great potential of use in biologically based food preservation systems. Despite the growing number of articles describing the isolation of bacteriocinogenic strains, genetic determinants for production, as well as the purification and biochemical characterization of these inhibitory substances, there are only limited reports of successful application of bacteriocins to meats.

This paper presents a critical review of the methods available for screening of bacteriocin-producing LAB strains from meats and also discusses the proposed mechanisms of action for LAB bacteriocins. Additionally, an overview of the Brazilian experience in the application of LAB bacteriocins to meats and meat products is given.     

Lactobacillus acidophilus: Characterization of the Species and Application in Food Production

L. acidophilus is a homofermentative, microaerophilic, short chain gram positive microorganism with rod morphology having its bacteriocins belonging to class II a. Several bacteriocins of L. acidophilus have been isolated and characterized. These are structurally similar, but their molecular weight varies as well as their spectrum of antimicrobial activity. They exhibit important technical properties, i.e., thermostability and retaining of activity at a wide pH range along with strong inhibitory actions against food spoilage and pathogenic bacteria make them an important class of biopreservatives. L. acidophilus can be added as an adjunct in many food fermentation processes contributing to unique taste, flavor, and texture. It also preserves the products by producing lactic acid and bacteriocins. A lot of new information regarding the bacteriocins of L. acidophilus has emerged during the last few years. In this review, an attempt has been made to summarize and discuss all the available information regarding the sources of bacteriocins production, their characteristics, and their antimicrobial action along with their application.     

Current Applications and Future Trends of Lactic Acid Bacteria and their Bacteriocins for the Biopreservation of Aquatic Food Products

This review emphasizes the importance of novel biopreservation strategies and their application to ensure seafood quality and safety especially within the context of increasing demand for minimally processed aquatic food products. The paper addresses the major hazards linked to spoilage and pathogenic bacteria found in fresh and processed aquatic foods, mainly ready-to-eat seafood subjected to short-term storage, and the biological strategies that can be used to minimize their growth. This is followed by an overview of current knowledge about the inhibiting bacteriocin-producing lactic acid bacteria isolated from aquatic food products or that is being evaluated for ensuring safety on seafood and seafood products as well as the characteristics of their bacteriocins. The different strategies for the biopreservation of aquatic food products, such as protective cultures or spray drying, and their current and future applications for the preservation of seafood products are also explored. Finally, novel antimicrobial active and intelligent packaging strategies based on antimicrobials film allowing controlled release of bacteriocins to refrigerated aquatic food products are also discussed.     

Bacteriocins and their Food Applications

Over the last 2 decades, a variety of bacteriocins, produced by bacteria that kill or inhibit the growth of other bacteria, have been identified and characterized biochemically and genetically. This review article focuses on the ecology of bacteriocins, determination of bacteriocin activity, biosynthesis of bacteriocins, and mode of action. Bacteriocin production and modeling are discussed in the article. Nisin is discussed in some detail in this article since it is currently the only purified bacteriocin approved for food use in the U.S. and has been successfully used for several decades as a food preservative in more than 50 countries. For activity spectra and food applications, the review article focuses primarily on class I and class IIa bacteriocins produced by lactic acid bacteria (LAB) given their development as food preservatives.     

FUNDAMENTALS AND PERSPECTIVES FOR THE USE OF BACTERIOCINS PRODUCED BY LACTIC ACID BACTERIA IN MEAT PRODUCTS

Bacteriocins of lactic acid bacteria (LAB) are proteinaceous compounds that may present antimicrobial activity towards important foodborne pathogens and spoilage-related microflora. Due to these properties, bacteriocin-producing strains or purified bacteriocins have a great potential of use in biologically based food preservation systems. Despite the growing number of articles describing the isolation of bacteriocinogenic strains, genetic determinants for production, as well as the purification and biochemical characterization of these inhibitory substances, there are only limited reports of successful application of bacteriocins to meats.

This paper presents a critical review of the methods available for screening of bacteriocin-producing LAB strains from meats and also discusses the proposed mechanisms of action for LAB bacteriocins. Additionally, an overview of the Brazilian experience in the application of LAB bacteriocins to meats and meat products is given.     

Plantaricin bacteriocins: As safe alternative antimicrobial peptides in food preservation—A review

Many peptides are excreted by gram-positive (+) and gram-negative (−) bacteria, possessing antimicrobial properties, called bacteriocins. Common bacterial species produce bacteriocins are called lactic acid bacteria. Nowadays, plantaricins are natural antimicrobial peptides produced by Lactobacillus plantarum strains have obtained special attention. The L. plantarum and their bacteriocins have got great importance in different areas as food biopreservatives and/or starters in dairy products, meat products, and fish products also, were used for treating diseases caused by pathogenic bacteria that is, reducing symptoms of irritable bowel syndrome disease (IBS) and decreasing the number of colonies of pathogenic bacteria in the wound-burning model in mice. Moreover, plantaricins have got a potent protective role against urinary tract infection (UTI). Although there are many studies on the types of bacteriocins and their purification and uses, such as Nisin and Pediocin, there have been no reports in the literature on the characterizations, production, and purification of plantaricins. The present review aims to describe plantaricins and some of their features and applications in general. Also mentioned are the most common methods of isolation and purification.     

Novel approaches to purifying bacteriocin: A review

ABSTRACT

Bacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.     

Class IIa bacteriocins from lactic acid bacteria: antibacterial activity and food preservation

In the last decade, a variety of ribosomally synthesized antimicrobial peptides, or bacteriocins, produced by lactic acid bacteria have been identified and characterized. As a result of these studies, insight has been gained into various fundamental aspects of biology and biochemistry such as bacteriocin processing and secretion, mechanisms of cell immunity, and structure-function relationships. In parallel, there has been a growing awareness that bacteriocins may be developed into useful antimicrobial food additives. Class IIa bacteriocins can be considered as the major subgroup of bacteriocins from lactic acid bacteria, not only because of their large number, but also because of their significant biological activities and potential applications. The present review provides an overview of the knowledge available for class IIa bacteriocins and discusses common features and recent findings concerning these substances. The activity and potential food applications of class IIa bacteriocins are a major focus of this review.     

细菌素的抑菌机制及其在食品工业中应用进展

由致病菌等微生物污染所引起的食源性疾病和食品腐败变质始终是食品工业面临的巨大难题,而传统的抗生素防腐剂所产生的细菌耐药性会对人体健康造成潜在的威胁。出于人们对于安全和绿色防腐剂的巨大需求,细菌素的研究愈发成为焦点,以期发现可有效控制食源性病原体的新型抗菌物质。细菌素是细菌分泌的多肽或前体多肽,分子量在1~100 ku之间不均匀分布,可以杀死或抑制同一生态系统中竞争营养物质的敏感细菌,少数细菌素还表现出抗病毒和抗真菌等特性。已有研究发现的细菌素具有不同的作用模式,例如：成孔、抑制细胞壁/核酸/蛋白质合成等。该研究综述了细菌素的种类与抑菌作用机制,并结合最新的细菌素在食品工业上的应用,全面概述了细菌素抑菌的特性及其对未来食品行业的应用前景与展望,为细菌素更好的应用在食品工业中提供一定的理论依据,同时对推动食品防腐保鲜技术的革新发展具有重要的意义。     

细菌素在食品贮藏保鲜中的应用

由微生物污染所引起的食品腐败变质问题是食品工业始终面临的巨大挑战之一。而传统的理化保鲜技术一方面会导致营养成分流失,另一方面对人体健康会造成潜在的威胁。人们一直在寻找一种安全、高效、天然的食品保鲜剂。现代生物技术的发展使得微生物保鲜剂逐渐进入人们的视野并不断地被开发、研究和应用。细菌素是由某些细菌分泌的一种具有抑菌活性的代谢产物。它无毒无抗性,能够在杀死微生物的同时最大程度地保留食品的鲜度和营养价值,可以替代化学防腐剂应用于食品保鲜,作为天然微生物源保鲜剂的一种,近些年受到了广泛关注。因此,本文简要介绍了细菌素的分类、特点,概述了各种类型的细菌素在不同种类食品保鲜方面的应用和研究进展,总结了在保鲜领域中存在的问题和挑战,并对其未来发展趋势提出展望,为细菌素更好地应用于食品工业提供一定的理论依据。     

Encapsulation systems for lutein: A review

BackgroundThe increased demand by consumers for clean labels has encouraged industry to search for replacements of synthetic ingredients in food products, and in particular, colorants. Lutein, a xanthophyll found in marigolds and corn, can be used in food products as a natural colorant replacing yellow food dyes. Moreover, lutein is considered a nutraceutical due to its potentially beneficial health effects, such as prevention of macular degeneration, role in the development of the visual and nervous systems of fetuses, and its antioxidant properties. However, incorporation of lutein into foods is often limited because of its low-water solubility, chemical instability, and poor oral bioavailability. For this reason, colloidal encapsulation systems have been developed to facilitate the incorporation of lutein into aqueous food and beverage products.Scope and approachThis review focuses on exploring encapsulation options for lutein using various emulsion-based, nanoparticle- and microparticle-based and molecular inclusion encapsulation systems, as well as additives that can be used to increase its chemical stability in these systems. This review covers all aspects of lutein encapsulation, including both food-grade and pharmaceutical-grade encapsulation systems.Key findings and conclusionsThough lutein-loaded encapsulation systems are extensively explored in this review, emulsions are of the most interest in industry as they are cost efficient and can be designed to increase the stability of lutein by selecting the proper emulsifiers and emulsification techniques. Despite the extensive amount of research carried out on the encapsulation of hydrophobic bioactive molecules such as lutein, there are still opportunities to develop encapsulation systems that further protect these molecules during storage and also increase their bioavailability after ingestion.     

Lactobacillus salivarius: Bacteriocin and probiotic activity

Lactic acid bacteria (LAB) antimicrobial peptides typically exhibit antibacterial activity against food-borne pathogens, as well as spoilage bacteria. Therefore, they have attracted the greatest attention as tools for food biopreservation. In some countries LAB are already extensively used as probiotics in food processing and preservation. LAB derived bacteriocins have been utilized as oral, topical antibiotics or disinfectants. Lactobacillus salivarius is a promising probiotic candidate commonly isolated from human, porcine, and avian gastrointestinal tracts (GIT), many of which are producers of unmodified bacteriocins of sub-classes IIa, IIb and IId. It is a well-characterized bacteriocin producer and probiotic organism. Bacteriocins may facilitate the introduction of a producer into an established niche, directly inhibit the invasion of competing strains or pathogens, or modulate the composition of the microbiota and influence the host immune system. This review gives an up-to-date overview of all L. salivarius strains, isolated from different origins, known as bacteriocin producing and/or potential probiotic.     

Preservation and fermentation: past,present and future

Preservation of food and beverages resulting from fermentation has been an effective form of extending the shelf-life of foods for millennia. Traditionally, foods were preserved through naturally occurring fermentations, however, modern large scale production generally now exploits the use of defined strain starter systems to ensure consistency and quality in the final product. This review will mainly focus on the use of lactic acid bacteria (LAB) for food improvement, given their extensive application in a wide range of fermented foods. These microorganisms can produce a wide variety of antagonistic primary and secondary metabolites including organic acids, diacetyl, CO2 and even antibiotics such as reuterocyclin produced by Lactobacillus reuteri. In addition, members of the group can also produce a wide range of bacteriocins, some of which have activity against food pathogens such as Listeria monocytogenes and Clostridium botulinum. Indeed, the bacteriocin nisin has been used as an effective biopreservative in some dairy products for decades, while a number of more recently discovered bacteriocins, such as lacticin 3147, demonstrate increasing potential in a number of food applications. Both of these lactococcal bacteriocins belong to the lantibiotic family of posttranslationally modified bacteriocins that contain lanthionine, beta-methyllanthionine and dehydrated amino acids. The exploitation of such naturally produced antagonists holds tremendous potential for extension of shelf-life and improvement of safety of a variety of foods.     

抗真菌性乳酸菌生物保护剂的研究进展

霉菌和酵母不仅引起果蔬、谷类、乳制品和肉制品等食品及农产品腐败变质,造成巨大的经济损失,而且霉菌还产生有害于人体健康的黄曲霉毒素、伏马菌素、单端孢霉烯、赭曲霉素A和棒曲霉素等真菌毒素,给食用者带来潜在的食品安全隐患。随着消费者对鲜活和微加工食品的需求不断增加,化学防腐剂在食品中应用受到限制,食品生物保护剂研究及应用已成为热点。乳酸菌通过生态位竞争、形成酸性环境和产生各种代谢产物对致病菌和腐败微生物具有较强的拮抗作用,作为一新型生物保护剂已广泛应用于各种食品中。本文对食品中抗真菌性乳酸菌的筛选和应用、乳酸菌产生的抗真菌代谢产物以及发展趋势进行综述,为进一步探究乳酸菌抗菌机理,研发高效食品生物保护剂提供借鉴与参考。     

Mining,heterologous expression,purification, antibactericidal mechanism,and application of bacteriocins: A review

Bacteriocins are generally considered as low-molecular-weight ribosomal peptides or proteins synthesized by G⁺ and G⁻ bacteria that inhibit or kill other related or unrelated microorganisms. However, low yield is an important factor restricting the application of bacteriocins. This paper reviews mining methods, heterologous expression in different systems, the purification technologies applied to bacteriocins, and identification methods, as well as the antibacterial mechanism and applications in three different food systems. Bioinformatics improves the efficiency of bacteriocins mining. Bacteriocins can be heterologously expressed in different expression systems (e.g., Escherichia coli, Lactobacillus, and yeast). Ammonium sulfate precipitation, dialysis membrane, pH-mediated cell adsorption/desorption, solvent extraction, macroporous resin column, and chromatography are always used as purification methods for bacteriocins. The bacteriocins are identified through electrophoresis and mass spectrum. Cell envelope (e.g., cell permeabilization and pore formation) and inhibition of gene expression are common antibacterial mechanisms of bacteriocins. Bacteriocins can be added to protect meat products (e.g., beef and sausages), dairy products (e.g., cheese, milk, and yogurt), and vegetables and fruits (e.g., salad, apple juice, and soybean sprouts). The future research directions are also prospected.     

Bacteriocin-based strategies for food biopreservation

Bacteriocins are ribosomally-synthesized peptides or proteins with antimicrobial activity, produced by different groups of bacteria. Many lactic acid bacteria (LAB) produce bacteriocins with rather broad spectra of inhibition. Several LAB bacteriocins offer potential applications in food preservation, and the use of bacteriocins in the food industry can help to reduce the addition of chemical preservatives as well as the intensity of heat treatments, resulting in foods which are more naturally preserved and richer in organoleptic and nutritional properties. This can be an alternative to satisfy the increasing consumers demands for safe, fresh-tasting, ready-to-eat, minimally-processed foods and also to develop "novel" food products (e.g. less acidic, or with a lower salt content). In addition to the available commercial preparations of nisin and pediocin PA-1/AcH, other bacteriocins (like for example lacticin 3147, enterocin AS-48 or variacin) also offer promising perspectives. Broad-spectrum bacteriocins present potential wider uses, while narrow-spectrum bacteriocins can be used more specifically to selectively inhibit certain high-risk bacteria in foods like Listeria monocytogenes without affecting harmless microbiota. Bacteriocins can be added to foods in the form of concentrated preparations as food preservatives, shelf-life extenders, additives or ingredients, or they can be produced in situ by bacteriocinogenic starters, adjunct or protective cultures. Immobilized bacteriocins can also find application for development of bioactive food packaging. In recent years, application of bacteriocins as part of hurdle technology has gained great attention. Several bacteriocins show additive or synergistic effects when used in combination with other antimicrobial agents, including chemical preservatives, natural phenolic compounds, as well as other antimicrobial proteins. This, as well as the combined use of different bacteriocins may also be an attractive approach to avoid development of resistant strains. The combination of bacteriocins and physical treatments like high pressure processing or pulsed electric fields also offer good opportunities for more effective preservation of foods, providing an additional barrier to more refractile forms like bacterial endospores as well. The effectiveness of bacteriocins is often dictated by environmental factors like pH, temperature, food composition and structure, as well as the food microbiota. Foods must be considered as complex ecosystems in which microbial interactions may have a great influence on the microbial balance and proliferation of beneficial or harmful bacteria. Recent developments in molecular microbial ecology can help to better understand the global effects of bacteriocins in food ecosystems, and the study of bacterial genomes may reveal new sources of bacteriocins.