Multi-Product Lactic Acid Bacteria Fermentations: A Review

Abstract

Industrial biotechnology is a continuously expanding field focused on the application of microorganisms to produce chemicals using renewable sources as substrates. Currently, an increasing interest in new versatile processes, able to utilize a variety of substrates to obtain diverse products, can be observed. A robust microbial strain is critical in the creation of such processes. Lactic acid bacteria (LAB) are used to produce a wide variety of chemicals with high commercial interest. Lactic acid (LA) is the most predominant industrial product obtained from LAB fermentations, and its production is forecasted to rise as the result of the increasing demand of polylactic acid. Hence, the creation of new ways to revalorize LA production processes is of high interest and could further enhance its economic value. Therefore, this review explores some co-products of LA fermentations, derived from LAB, with special focus on bacteriocins, lipoteichoic acid, and probiotics. Finally, a multi-product process involving LA and the other compounds of interest is proposed.Fermentation 2020, 6, 23 2 of 21 by-products, were proposed to improve industrial single-product biotechnological processes [2]. One example is the use of cellulose and hemicellulose from sugarcane bagasse (a residue obtained during the bioethanol production and usually used for energy generation) for the production of value-added chemicals [3]. Likewise, glycerol, a by-product of the biodiesel industry with low value in the market, is targeted as a molecule of interest in fermentation processes. Such multi-product processes, based on the conversion of renewable materials into biobased products, are known as biorefineries [4].The study, development, and application of robust microbial strains, able to utilize a variety of substrates and to produce a wide range of products, is considered a milestone in the development of biorefineries [4]. Lactic acid bacteria (LAB) are a diverse group with recognized potential for the development of integrated biorefineries [5]. LAB are non-sporulating, non-motile, acid-tolerant, non-respiring but aerotolerant, catalase-negative, Gram-positive cocci or rods. They are characterized by the production of lactic acid (LA) as the major end metabolic product of carbohydrate fermentation [6][7][8][9]. Given the lack of a functional respiratory system, LAB obtain energy through substrate-level phosphorylation following two metabolic pathways for hexose fermentation, i.e., homofermentative and heterofermentative. As shown in Figure 1, the first pathway is based on glycolysis with the production of mainly LA, whereas the second one, known as the pentose phosphate pathway, is characterized for the production of CO 2 and ethanol, or acetate in addition to LA [6].

Selection of Wild Lactic Acid Bacteria Strains as Promoters of Postbiotics in Gluten-Free Sourdoughs

“…In addition, the inflammatory reactions of gluten can be minimized by the metabolic activity of LAB strains that hydrolyze the substrate proteins into small fractions without side-effects for the CD patients [24,[29][30][31]. Lactic acid bacteria (LAB) occur naturally in many fermented foods, such as sourdoughs and dairy products, and both the microorganisms and their metabolites are classified as Generally Regarded as Safe (GRAS) and Qualified Presumption of Safety (QPS)-thus being considered as non-toxic and food-grade microorganisms [32,33].…”

Production of Lactic Acid from Seaweed Hydrolysates via Lactic Acid Bacteria Fermentation

“…Lactic acid, a colorless and odorless monocarboxylic acid [1], has received considerable attention owing to its various applications in food and non-food industries [2]. For example, there has been an increasing demand of lactic acid in the manufacturing of biodegradable polylactic acid materials used as an alternative to petroleum-derived plastics [3]. It was estimated that the worldwide demand for lactic acid would reach 1,000,000 metric tons by the year 2020 [4].…”

Production of Lactic Acid from Carob, Banana and Sugarcane Lignocellulose Biomass

“…Lignocellulosic residues are composed of cellulose, hemicellulose, and lignin. Pretreatments are required, followed by enzymatic hydrolysis processes, where the released sugars are utilized for the production of economical products including bioethanol, bacteriocins, lipoteichoic acid, probiotics, biogas and LA [1][2][3][4]. The bioconversion of lignocellulose to LA is an important alternative for its valorization to produce LA to be utilized in food, cosmetic and pharmaceutical industry [4,5].…”

“…Pretreatments are required, followed by enzymatic hydrolysis processes, where the released sugars are utilized for the production of economical products including bioethanol, bacteriocins, lipoteichoic acid, probiotics, biogas and LA [ 1 , 2 , 3 , 4 ]. The bioconversion of lignocellulose to LA is an important alternative for its valorization to produce LA to be utilized in food, cosmetic and pharmaceutical industry [ 4 , 5 ]. The global demand for LA is increasing, with its demand expected to reach 1,960 kilotons by 2025 [ 6 , 7 , 8 ].…”