Enhancement of the antioxidant and antimicrobial activities of maize wastewater by an eco-friendly process

Nejayote is a highly polluting wastewater discarded after the nixtamalization process of maize (Zea mays L.). It contains many organic compounds and unused nutrients. In this study, we optimized the biological treatment of nejayote through Bacillus clausii-induced fermentation, using the response surface methodology, to enhance the content of bioactive compounds, antioxidant and antimicrobial activities of nejayote. The optimal fermentation temperature and time were 36 °C and 4.8 days, respectively, which produced a biomass of 9.1 log10 CFU mL−1 of B. clausii, total phenolic content of 524 mg equivalents of gallic acid per 100 mL sample, and antioxidant activity of 2876 µmol equivalent of trolox per 100 mL sample. The fermentation significantly increased the total phenolic content (~ 150%) and antioxidant activity (~ 30%), increased the content of 8-O-4-hydrodiferulic, 8-O-4-hydrotriferulic, and ferulic acids, and synthesized caffeic acid when compared with non-fermented nejayote. The fermentation process improved the antimicrobial activity of nejayote against Salmonella Typhimurium (3.5-fold) and Enterococcus faecalis (2.72-fold) after 12 h as compared to non-fermented nejayote. B. clausii-fermented nejayote obtained by this alternative eco-friendly process is thus a product with increased bioactive properties that could be used as functional ingredient in different food products.