Direct Fermentation of Fishmeal Wastewater and Starch Wastewater to Lactic Acid by Rhizopus Oryzae

Fishmeal wastewater (FWW) and starch wastewater (SWW), without additional nutrients, were investigated for the direct lactic acid production using 2 strains of Rhizopus genus. R. oryaze AS 3.254 could use FWW and SWW simultaneously for lactic acid production and fungal growth while R. oryaze 3.41 only utilized this complex for fungal growth. For R. oryaze AS 3.254, the optimal C/N for lactic acid production was 100:1. R. oryaze 3.41 could produce lactic acid by use of glucose and FWW and the optimal C/N was 124. Both fungi showed higher biomass production at lower C/N. The direct lactic acid production from SWW and FWW by R. oryaze AS 3.254 was characterized by starch hydrolysis, accumulation of reducing sugars, COD and nitrogen removal, and production of lactic acid and fungal biomass. Starch hydrolysis could arrive at 1.23 g/L-h while COD and nitrogen removal were 96.2% and 89.4%, respectively at fermentation time 88 h. The highest lactic acid yield was 0.674 g COD/g COD based on the equivalent COD of SWW and FWW associated with 2.65 g/L fungal biomass at fermentation time 72 h while the maximum productivity 0.783 g/L-h was obtained at fermentation time 40 h.