Production of acetone-butanol-ethanol and lipids from sugarcane molasses via coupled fermentation by Clostridium acetobutylicum and oleaginous yeasts

Abstract

Acetone-butanol-ethanol (ABE) and lipids were produced from sugarcane molasses via coupled fermentation by Clostridium acetobutylicum and oleaginous yeasts. ABE fermentation of sugarcane molasses with varying sugar concentrations (50–100 g/L) was investigated, and the wastewaters were analyzed and classified into two types based on their carbon source content and structure. Then, four oleaginous yeasts were cultured on the two types of ABE fermentation wastewaters respectively, and their lipid productions, removals of COD and ammonia were investigated and evaluated. It was found that via coupling with lipid-producing fermentation process, the ABE fermentation wastewaters rich in organic acids could be effectively treated, the added value of the products obtained could be increased, meanwhile, the sugar load and treatment efficiency of the whole system could be improved. Specifically, ABE fermentation by C. acetobutylicum CH012 could be carried out normally on 50–80 g/L of total sugars. The maximum solvents production, which was 19.640 g/L (5.580 g/L acetone, 13.159 g/L butanol and 0.901 g/L ethanol) with a corresponding yield of 0.335 g/g, was obtained at 70 g/L sugars. Wastewater (from the ABE fermentations performed at 50–60 g/L sugars) containing low concentrations (＜3 g/L) of sugars and taking organic acids as dominant carbon source was defined as Type-1, while wastewater (from the ABE fermentations performed at 70–80 g/L sugars) containing high concentrations (10–20 g/L) of sugars and taking sugars as dominant carbon source was defined as Type-2. Trichosporon dermatis could performed well on both Type-1 and Type-2 wastewaters in terms of lipids production and removals of COD and ammonia. Lipomyces starkeyi did not adapt to Type-1 wastewater, but when culturing on Type-2 wastewater, it achieved the highest lipid production of 2.37 g/L with COD and ammonia nitrogen removal rate of 64.62 % and 57.09 % respectively.