KINETIKA DAN VARIABEL OPTIMUM FERMENTASI ASAM LAKTAT DENGAN MEDIA CAMPURAN TEPUNG TAPIOKA DAN LIMBAH CAIR TAHU OLEH RHIZOPUS ORYZAE

Abstract

Compounding of tapioca flour and tofu liquid waste can be used an alternative medium fermentation which is cheap to produce lactic acid by using Rhizopus oryzae fungus. Rhizopus oryzae has ability to sustain saccharification process and fermentation (SSF, Simultaneous Saccharification and Fermentation) in single stage. The objectives of research were studying the characteristic of tapioca flour and tofu liquid waste as medium of lactic acid production by Rhizopus oryzae fungus, investigating effect of C/N ratio an agitation speed on biomass growth and lactic acid production, determining kinetic parameters of lactic acid fermentation i.e. specific growth rate (μ), maximum specific growth rate (μm), substrate saturation constant (Ks), substrate consumption constant (k3), yield of biomass to substrate (YX/S) and yield of product to substrate (YP/S), analyzing optimum amylum concentration and optimum agitation speed for biomass growth and lactic acid production. The lactic acid fermentation was done in 250 ml Erlenmeyer flasks containing 100 ml final volume of medium production. Furthermore medium production was inoculated with 7 ml of seed culture. It was put in incubator shaker with temperature of 30 0C, pH of ± 6 for 72 hours. From that experiment several data was found i.e. profile, parameter of kinetic, optimum relative of C/N ratio and agitation speed. Besides, this research used a 22 full factorial composite design and data processing by Response Surface Methods to obtain effect and optimum condition of amylum concentration and agitation speed on biomass and lactic acid concentration. The results showed that tofu liquid waste has nitrogen content which is sufficient to produce lactic acid of 5 g/l, and a relatively low carbon content of 1.1 g/l. That needed additional C element from other source. Optimum relative of C/N ratio and agitation speed for biomass growth and lactic acid production was 2.4-3.2 and 150 rpm respectively, μm was 0.046 hr1, Ks was 4.324 g/l , maximum k3 was 0,031 hr-1, maximum YX/S was 0.182 and maximum YP/S was 0.415. Maximum biomass concentration was 6 g/l at amylum concentration of 43 g/l and agitation speed of 176 rpm. Maximum lactic acid concentration was 8.26 g/l at amylum concentration of 40 g/l and agitation speed of 139 rpm. Keywords: tapioca flour, tofu liquid waste, Rhizopus oryzae, lactic acid.