Culture of complex bioflocculant-producing strains and optimization of its nutritional conditions by using cassava starch wastewater

A new style of combined microbial flocculant and a new way for cassava starch wastewater reutilization were proposed. Two lactic acid bacterial strains LB3 and LB5 which could produce bioflocculant with high flocculating to cassava starch wastewater were screened from anaerobic wastewater. 16 S r DNA gene sequence analysis showed that the two strains could be identified as Lactobacillus casei and Lactobacillus plantarum respectively. The nutritional conditions which combined strains fermented cassava starch wastewater to produce bioflocculant were optimized through single factor test. The optimization nutritional compositions were :raw concentration cassava starch wastewater without adding KH_2PO_4,with glucose as the optimal carbon source in wastewater culture medium,combined nitrogen source of yeast extract and peptone by 1∶2,4.5% of total carbon and nitrogen amount with C/N ratio of 1.5. With the condition above,the flocculation rate of fermentation broth to starch wastewater and Kaolin clay suspension was found to be 89.2% and 91.4% respectively.