Organic fraction of municipal solid waste as a suitable feedstock for the production of lipid by oleaginous yeast Cryptococcus aerius

Abstract

The detoxified pre-hydrolysate and enzymatic hydrolysate of OFMSW were used as substrates for lipid production by Cryptococcus aerius. Factorial experimental designs were employed for the optimization of dilute acid pre-hydrolysis, detoxification by over-liming, enzymatic hydrolysis, and lipid production. OFMSW pre-hydrolysis with 3% H2SO4 for 45min was found to be the optimal treatment, resulted in total sugar concentration of 65.5g/L (32.8% yield, based on grams of total reducing sugar per gram of OFMSW). The optimal detoxification conditions of the pre-hydrolysate by over-liming was incubation at 30°C and pH 11 for 24h, resulted in the reduction of total nitrogen, total phenolic compounds, and furans by 51.3%, 45.1%, and 100%, respectively. The residual solid was subjected to enzymatic hydrolysis, and the highest sugar concentration of 30.5g/L was obtained. At optimal conditions, the yeast cultivation on the detoxified pre-hydrolysate and enzymatic hydrolysate resulted in the lipid production of 3.9g/L (12.8% yield, based on g lipid per g consumed sugar) and 4.3g/L (17.1% yield, based on g lipid per g consumed sugar), respectively. The elemental analysis showed the presence of heavy metals including iron (925mg/l), zinc (59mg/l), lead (4.7mg/l), and nickel (3.5mg/l) in the pre-hydrolysate, which were significantly reduced by the over-liming detoxification.