L-Lactic Acid Fermentation from Raw Cassava with Tofu liquid waste medium

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Batch fermentation by streptococcus bovis was carried out in order to investigate the characteristics of L-lactic acid fermentation from raw cassava with tofu liquid waste (TLW) medium. The use of cassava-TLW system is intended to produce low cost L-lactic acid for the production of polylactic acid, a polymer used as biodegradable plastic, since cassava is cheap raw material, and TLW is free cost medium. Raw-cassava as substrate was compared with glucose and tapioca at concentration of 1wt%. TLW medium was compared with both of trypto-soya broth (TSB) as a standard med ium and water as a blank medium. In order to maintain pH not to be lower than 5.0, 2 mol equivalent calcium carbonate (CaCO_3) were added at initial fermentation. In comparison with the standard system glucose-TSB, the high level of lactic acid concentration from cassava-TLW was obtained about 75±5%, and its productivity was 1/3〜1/2 of the standard system. The maximum of lactic acid obtained with addition CaCO_3 in TSB and TLW medium were 2.2 times and 1.6 times, respectively higher than that from TSB without CaCO_3 addition. Furthermore, experiments were also carried out in TLW with different concentrations of saccharide, i.e.:5,10, 15, 20 wt% to investigate its effect on the lactic acid production. The maximum lactic acid concentrations was found to be in order : cassava (6.66 wt%)> tapioca (5.36 wt%) > glucose (3.41 wt%) were reached at 10 wt% of saccharide concentration