초록
Spent digester streams were reformulated into nutrient rich effluents, capable of supporting biotechnological production of platform chemicals. This was achieved, using a set of physical pre-treatments including, sedimentation, dilution and sieving, followed by cross-flow microfiltration processing to give particle and cell free nutrient streams with a C:N:P molar ratio of 1:1.35:0.03. These streams were inoculated on bench scale, with Clostridium butyricum NCIMB 7432, a well-known acids producer, giving good growth rates (μ<SUB>max</SUB> 0.24 h<SUP>-1</SUP>) and acids concentrations of 110 mM acetic acid and 18 mM per litre butyric acid. When the treated effluent was fortified with 2% w/v glucose there was a significant improvement with a 0.38 h<SUP>-1</SUP> μ<SUB>max</SUB> and platform chemicals concentration of 279 mM acetic acid and 32 mM butyric acid per litre. These media gave comparable performance with the synthetic media, therefore demonstrating a valid alternative solution to commercial media preparations. The cost of treating the excess digestate by microfiltration within the scope of formulation to nutrient media has been calculated at 0.0033 $USD/kg, 3 times lower than the cost of production of nutrient media.