This work focused on the lactic acid production from acidogenic fermentation of fruit and vegetable
wastes treatment. A long term completely stirred tank reactor (CSTR) lasting for 50 days was operated
at organic loading rate (OLR) of 11 gVS/(L d) and sludge retention time (SRT) of 3 days with pH controlled
at 4.0 (1–24 day) and 5.0 (25–50 day). The results indicated that high amount of approximately 10–20 g/L
lactic acid was produced at pH of 4.0 and the fermentation type converted from coexistence of homofer-mentation and heterofermentation into heterofermentation. At pH of 5.0, the hydrolysis reaction was
improved and the total concentration of fermentation products increased up to 29.5 gCOD/L. The hetero-fermentation was maintained, however, bifidus pathway by Bifidobacterium played an important role.
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