Yeast Compound for Single-cell Protein Production by Potato Starch Processing Wastewater Fermentation

Abstract

To collect single cell protein (SCP) and remove chemical oxygen demand (COD) from potato starch processing wastewater, five industrial yeasts, i.e. Geotrichum candidum link, Candida utilis, Saccharomycopsis fibuligera, Candida tropicalis and Saccharomyces cerevisiae were selected for the fermentation of the wastewater. The efficiency in SCP yield and COD removal of the five yeasts and their combination were evaluated, respectively. The results showed that C. utilis was the best strain for potato starch processing wastewater fermentation. After fermenting for 12 h at an initial pH 6 and 28℃ with an initial COD of 12594 mg·L-1 and an inoculated ratio of 10% (v/v), its SCP yield, water-soluble protein (WSP) yield and COD removal reached 1.87 g·L-1, 0.274 g·L-1 and 40.22%, respectively. The co-culturing of the yeasts that were significant difference in nutrition and metabolic property could maximize the conversion and utilization of various organic substances in the wastewater, resulting in a better COD removal and SCP production. It was found that the mixture of C. utilis, G. candidum link and C. tropicalis was the best combination for the fermentation of potato starch processing wastewater. Fermented under the same conditions as that of C. utilis, the COD removal rate of the three-strain mixture averaged 46.97%, and a SCP yield of 2.48 g·L-1 and a WSP yield of 0.398 g·L-1 were obtained, which were 1.17, 1.33 and 1.45 times of C. utilis respectively.