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].

Lactic acid bacteria (LAB) with potential for the development of multi-product processes are necessary for the valorization of side streams obtained during the biotechnological production of lactic acid (LA). In this study, 14 LAB strains isolated from pineapple agro-industrial residues in Costa Rica were cultivated in microplates, and the six strains with the highest growth were selected for fermentation in microbioreactors to evaluate the production of LA and acetic acid, and the consumption of glucose. Lacticaseibacillus paracasei 6710 and L. paracasei 6714 presented the highest OD600 values (1.600 and 1.602, respectively); however, the highest LA (in g/L) production was observed in L. paracasei 6714 (14.50 ± 0.20) and 6712 (14.67 ± 0.42). L. paracasei 6714 was selected for bioreactor fermentation and reached a maximum OD600 of 6.3062 ± 0.141, with a LA yield of 84.9% and a productivity of 1.06 g L−1 h−1 after 21 h of fermentation. Finally, lipoteichoic acid (LTA) detection from biomass was performed and the antimicrobial activity of the compounds present in the supernatant was studied. LTA was detected from L. paracasei 6714 biomass, and its supernatant caused significant inhibition of foodborne surrogate microorganisms. LAB isolated from pineapple silage have biotechnological potential for multiproduct processes.