Lactic acid production from potato peel waste by anaerobic sequencing batch fermentation using undefined mixed culture

Lactic acid (LA) is a necessary industrial feedstock for producing the bioplastic, polylactic acid (PLA), which is currently produced by pure culture fermentation of food carbohydrates. This work presents an alternative to produce LA from potato peel waste (PPW) by anaerobic fermentation in a sequencing batch reactor (SBR) inoculated with undefined mixed culture from a municipal wastewater treatment plant. A statistical design of experiments approach was employed using set of 0.8 L SBRs using gelatinized PPW at a solids content range from 30 to 50 g L−1, solids retention time of 2-4 days for yield and productivity optimization. The maximum LA production yield of 0.25 g g−1 PPW and highest productivity of 125 mg g−1 d−1 were achieved. A scale-up SBR trial using neat gelatinized PPW (at 80 g L−1 solids content) at the 3 L scale was employed and the highest LA yield of 0.14 g g−1 PPW and a productivity of 138 mg g−1 d−1 were achieved with a 1 d SRT.