Pre-treating anaerobic mixed microflora with waste frying oil: A novel method to inhibit hydrogen consumption

An innovative method was introduced to inhibit methanogenic H₂ consumption during dark fermentative hydrogen production by anaerobic mixed cultures. Waste frying oil was used as an inhibitor for hydrogenotrophic methanogens. Simultaneous effect of waste frying oil concentrations (0-20 g/L) and initial pH (5.5, 6.5 and 7.5) on inhibition of methanogenic H₂ consumption and enhancement of H₂ accumulation were investigated using glucose as substrate. Enhanced hydrogen yields with decreased methane productions were observed with increasing the waste frying oil concentrations. On average, CH₄ productions from glucose in the cultures received 10 g/L WFO were reduced by 88%. Increased WFO concentration up to 20 g/L led to negligible CH₄ productions and in turn enhanced H₂ yields. Hydrogen yields of 209.26, 195.35 and 185.60 mL/g glucose_added were obtained for the cultures pre-treated with 20 g/L waste frying oil with initial pH of 5.5, 6.5 and 7.5 respectively. H₂ production by pre-treated cultures was also studied using a synthetic food waste. Anaerobic mixed cultures were pre-treated with 10 g/L WFO and varying durations (0, 24 and 48 h). A H₂ yield of 71.46 mL/g VS was obtained for cultures pre-treated with 10 g/L WFO for 48 h that was 475% higher than untreated control. This study suggests a novel and inexpensive approach for suppressing hydrogenotrophic methanogens during dark fermentative H₂ production.