Bioconversion of Corn Steep Liquor to Biofertilizer by Symbiotic Fermentation

Abstract

Corn Steep Liquor (CSL) is wastewater from corn starch industry. The huge amount generation made it as a serious environmental problem. But CSL is nutrient-rich with diverse amino acids and other trace elements. In this study, symbiotic biofertilizer was studied using CSL as main substrate. In this study, 9 industrial strains, which were recognized as high performance species in the biofertilizer industry were collected, including four bacillus, four fungus and one yeast species. Three dominant strains were selected finally, depending on the ability to dissolve phosphorus, ability for protein hydrolysis and cell growth. They were Bacillus subtilis 3301, Bacillus licheniformis and Aspergillus Niger. The results expressed that the highest growth cell count of Bacillus subtilis 3301 reached 3.1×109 CFU/mL, the highest protein hydrolysis capacity of Bacillus licheniformis reached 600 mg/L and the highest phosphorus-dissolving capacity of Aspergillus Niger reached 1100 mg/L respectively. Then, symbiotic fermentation of the three strains was carried out both in shake-flask culture and fermentation tank (5 L). Interestingly, series of significant data of symbiotic fermentation were obtained, which were different from individual cultures. Especially, the total growth cell count in the 5 L scale fermenter culture was higher than individual cultures, which proved the mutual promotion effect between different strains. This research would provide a new view to utilize the waste of corn steep liquor as high value-added agricultural products.