Fermentation as a Strategy for Bio-Transforming Waste into Resources: Lactic Acid Production from Agri-Food Residues

Abstract

Lactic acid (LA) obtained by fermentation of carbohydrates is well-known and widely used in the food sector. This process is as an alternative to the chemical synthesis and ensures several advantages especially in terms of environmental sustainability. In particularly, the opportunity to use agro-food residues as fermentable raw materials could improve the overall process sustainability, without considering the indisputable advantages in terms of waste reduction and residual biomass valorization, in a bio- and circular economy perspective. This research deals with the study and development of the fermentation processes of various waste biomasses from the agro-food industries, including milk whey (MW), ricotta cheese whey (RCW), pear processing residues (PPR), potato pomace (PP), tomato pomace (PT), in order to obtain an experimental protocol applicable to the production of LA. Lactobacillus casei DSM 20011 (ATCC 393), a homofermentative L(+)-LA producing bacterium has been used, starting from small-scale tests to verify of the microorganism to grow in complex medium with different carbon sources and the possible presence of potentially toxic substances for microbial growth. Yields from 27.0 ± 0.3% to 46.0 ± 0.7% have been obtained. Then, a scaling-up was performed in a 1 L batch fermenter, using a mixed medium of RCW and PPR in different ratio. The best LA yield was 78.3% with a volumetric productivity of 1.12 g/L·h in less than 60 h.

Optimization of Lactic Acid Production from Pineapple By-Products and an Inexpensive Nitrogen Source Using Lactiplantibacillus plantarum strain 4O8

“…The VP aforementioned (1:308 ± 0:01 g/l h) is higher than the one obtained (0:331 g/l h) by Mufidah and Wakayama [12] who, in the course of their work, used a lactic acid bacteria and a fungi strains for LA production from banana peel. Similarly, the most important LA productivity (1.12 g/l/h) reported by Costa et al [36] in their study on lactic acid production from agri-food residues as carbon sources is lower than that highlighted in the present work. The use of carob, banana, and sugarcane lignocellulose biomass for LA production was the subject of a study conducted by Azaizeh et al [37]; it revealed that LA production from these carbohydrate substrates with yeast extract were 54.8 g/l, 26.6 g/l, and 46.5 g/l, It was found that the production of LA would depend on nature and chemical composition of the carbohydrate and protein substrates in the fermentation broth and would also depend on the fermentation strain and fermentation conditions [3,7,10,38].…”

Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation

“…Electron donors are oxidized to provide electrons (e.g., NADH) and acetyl-CoA for the RBO pathway where two acetyl-CoA are elongated to even-chain carboxylates, e.g., n-butyrate (nC4), n-caproate (nC6), or n-caprylate (nC8). Lactate is an interesting electron donor that can be easily obtained from residual biomass materials [3][4][5] and has been successfully converted to n-caproate [4,[6][7][8]. Alternatively, reactor microbiomes may convert lactate to propionate and acetate [9].…”

Microbial Resources, Fermentation and Reduction of Negative Externalities in Food Systems: Patterns toward Sustainability and Resilience

“…Some studies proposed pathways towards enhanced nutrient bioavailability [10,[58][59][60] and improved human health/well-being [61][62][63][64] (including microbiome therapies [63][64][65][66]), advances of interest to contrast the adverse effects of some negative externalities. Furthermore, the design of several works looking at reducing resource dissipation, saving energy [52,69], valorising foods by-products [52,70,71], foods wastes [72][73][74], and wastewater [75][76][77]. Finally, some strategies can preserve microbial diversity associated with food fermentation [78][79][80].…”