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

•Lipid production by a robust yeast strain capable of using organic fraction of municipal solid waste.•The MSOW introduced as suitable source for biodiesel production by yeast fermentation.•Dilute acid and enzymatic hydrolysis, detoxification and lipid production were optimized.•The heavy metals were reduced by the over-liming detoxification.•The produced single cell oil by Cryptococcus aerius was similar to that of plant oils.

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 45 min was found to be the optimal treatment, resulted in total sugar concentration of 65.5 g/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 24 h, 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 30.5 g/L was obtained. At optimal conditions, the yeast cultivation on the detoxified pre-hydrolysate and enzymatic hydrolysate resulted in the lipid production of 3.9 g/L (12.8% yield, based on g lipid per g consumed sugar) and 4.3 g/L (17.1% yield, based on g lipid per g consumed sugar), respectively. The elemental analysis showed the presence of heavy metals including iron (925 mg/l), zinc (59 mg/l), lead (4.7 mg/l), and nickel (3.5 mg/l) in the pre-hydrolysate, which were significantly reduced by the over-liming detoxification.

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