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The aim of this study was to perform the adaptation of Lactobacillus paracasei NRRL B-4564 to substrate through adaptive evolution in order to ensure intensive substrate utilization and enhanced L (+)-lactic acid (LA) production on molasses-enriched potato stillage. To evaluate the strain response to environmental conditions exposed during the adaptation process and to select the best adapted cells, the antioxidant activity and LA-producing capability were assessed in batch fermentation. The most promising adapted strain was further used in a pulsed fed-batch mode. Among three selected adapted strains, L. paracasei A-22 showed considerably improved antioxidant capacity, demonstrating more than onefold higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging rates compared to parent strain. This strain also exhibited superior LA production in batch fermentation and reached 89.4 g L of LA, with a yield of 0.89 g g, a productivity of 1.49 g L h, and an optical purity greater than 99%. Furthermore, in fed-batch mode L. paracasei A-22 resulted in 59% higher LA concentration (169.9 g L) compared to parent strain (107.1 g L). The strain adaptation to molasses environment, performed in this study, is a rather simple and promising method for enhancement of LA production on the complex agro-industrial substrate.

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BACKGROUND: Growing challenges of resource depletion, food security and environmental protection are putting stress on the development of biorefinery processes for bioprocessing of residues from food and agro-industry into value-added products. In this study, the simultaneous production of lactic acid (LA) and livestock feed on a combined substrate based on molasses and potato stillage by Lactobacillus paracasei NRRL B-4564 immobilized onto sunflower seed hull (SSH), brewer's spent grain (BSG) and sugar beet pulp (SBP) was studied. RESULTS:The highest total LA concentration of 399 g L −1 with overall productivity of 1.27 g L −1 h −1 was achieved in repeated batch fermentation by SBP-immobilized biocatalyst, followed by BSG-and SSH-immobilized cells. Fermentation improved the content of proteins and ash, and decreased the content of fibers in all three support materials. In addition, the fermentation had favorable effect on in vitro dry matter digestibility and energy values of SSH and BSG. According to assessment of probiotic potential, L. paracasei demonstrated a favorable probiotic profile, exhibiting high resistance to simulated ruminant digestive tract and significant antioxidant and antimicrobial activity. CONCLUSIONS: The proposed strategy enables valorization of agro-industrial residues as value-added ruminant feed and simultaneous LA production. Following principles of circular economy, the developed process combines different raw materials and integrates them into a biorefinery process, improving the overall profitability and productivity. Probiotic potential of L. paracasei NRRL B-4564Phenotypic characteristics, such as survival in simulated conditions of GIT, antimicrobial and antioxidant activity, as well as J Sci Food Agric 2019; 99: 5293-5302

BACKGROUND: Brewer's spent grain (BSG), brewer's yeast (BY), malt rootlets (MR), and soy lecithin (SL) are valuable and abundant by-products obtained from brewing, malting, and oil industry, respectively. L-(+)-lactic acid (LA) is organic acid that has wide range of application. In this study hydrolysate obtained from BSG and MR mixture (BSGMR), was used in combination with SL and BY extract (BYE) in LA fermentation. The aim was to evaluate the effect and optimize the addition of SL (0.1 and 0.2%) or BYE (10 and 20%) compared to Tween 80 (0.1%) and yeast extract (0.8%), in batch and fed-batch LA fermentation. RESULTS: Using optimal SL and BYE concentrations (0.19 and 19.12%, respectively) obtained by response surface methodology (RSM) highest LA concentration, yield, and volumetric productivity

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