Abstract
Food waste and municipal sludge were used as the substrates for the biosynthesis of lactic acid in a batch fermentor. The probiotic bacterial strain Lactobacillus rhamnosus AW3 isolated from date processing waste was used to produce lactic acid in a batch fermentor. Co-fermentation enhanced the biosynthesis of lactic acid and decreased substrate inhibition more than mono-substrate fermentation. A maximum yield of 28.4 ± 0.87 g/L of lactic acid was obtained through co-fermentation of food waste and municipal sludge at an optimized ratio of 2:0.5. Lactic acid production was improved by the supplementation of fructose, peptone, and sodium dihydrogen phosphate at pH 5.5 after 48 h fermentation. This production was approximately three-fold higher than that during mono-fermentation of food waste. The tested bacterial strains were obtained from the Microbial Type Culture Collection (MTCC). Lactic acid showed potent antimicrobial activity against pathogenic organisms, such as Bacillus subtilis MTCC 5981 (14 mm), Staphylococcus aureus MTCC 737 (20 mm), Pseudomonas aeruginosa MTCC 424 (24 mm), Enterobacter aerogenes MTCC111 (19 mm), Escherichia coli MTCC 443 (18 mm), Penicillium chrysogenum MTCC 5108 (19 mm), and Aspergillus niger MTCC 282 (19 mm). The antimicrobial properties of lactic acid have significant potential to inhibit the growth of pathogenic bacteria and fungi and improve probiotic properties. The lactic acid extracted from L. rhamnosus AW3 decreased the pH value of soil (p < 0.01) and increased the availability of soil phosphorus (p < 0.01). These findings demonstrate the bioconversion of food waste and municipal sludge into lactic acid, and the recycling of food wastes in urban areas to enhance soil nutrients.
Highlights
Biomass valorization is the process of converting biomass into highly useful materials including fuels and chemicals
These lactic acid bacteria (LAB) species isolated from various food products can be effectively utilized in the formulation of functional foods to manage the growth of pathogenic bacteria and indirectly control various diseases that may affect consumers [42]
Lactic acid was produced from food waste (FW) and municipal sludge (MS) in a batch fermentor
Summary
Biomass valorization is the process of converting biomass into highly useful materials including fuels and chemicals. In European Union, food waste generation increased every year and it changed in each stage of food supply chain. 25% of food waste generated in the food supply chain and this percentage increased as 40% during postharvest and processing stage. Food waste is one of the major environmental problems, with waste and losses generated at every stage of the food supply chain. Food supply chain begins with the agriculture and livestock sector, which generated various by-products This early stage of supply chain produces food waste and food loss in the form of very low-quality products and products with no commercial value. Food waste generation continues even at the final stage (bad storage or preservation) These substrates are highly suitable to be treated by anaerobic digestion because of high moisture content and solid and simple carbohydrates [8]. The generation of high value-added products from food wastes is highly desirable
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