Non-sterile fermentation of food waste with indigenous consortium and yeast – Effects on microbial community and product spectrum

[Display omitted] •Lactic acid and ethanol were simultaneously produced from food waste.•The yield of each product can be controlled by varying pH.•Neutral pH favors lactic acid, while acidic pH is beneficial for ethanol formation.•Changes during fermentation were discussed on product- and producer levels. This work presents examples of non-sterile mixed culture fermentation of food waste with a cultivated indigenous consortium (IC) gained from food waste, which produces lactic and acetic acids, combined with Saccharomyces cerevisiae, which produces ethanol. All results are flanked by microbial analysis to monitor changes in microbial community. At pH 6 and inoculated with yeast or IC, or both mixed sugars conversion was equal to 71%, 51%, or 67%, respectively. Under pH unregulated conditions metabolic yields were 71%, 67%, or up to 81%. While final titer of acetic acid was not affected by pH (100–200 mM), ethanol and lactic acid titers were. Using mixed culture and pH 6, sugars were almost equally used for formation of ethanol and lactic acid (400–500 mM). However, under pH unregulated conditions 80% of the substrate was converted into ethanol (900–1000 mM).