Optimization of biobutanol production by clostridium species upm-a1 with liquid central composite design (ccd)

Abstract

Optimization of biobutanol production by Clostridium species UPM-A1 was conducted using Central Composite Design (CCD) with liquid pineapple waste as carbon source. The Design Expert® Software (State-Ease Inc., 2021 Ease Hennepin Ave, Suite 191, Minneapolis, MN, 55413) Version 6.0.4 was employed for generating the experimental design which consisted of three significant parameters, including temperature, yeast extract, and pH. The design consisted of twenty different experiments including six replicates at central points. The experiments were conducted in accordance with the conditions provided by the software, during which highest biobutanol production was attained at run three with temperature 42.50°C, yeast extract 2.14g/L, pH 5.5, and a total biobutanol concentration value of 0.441 g/L. Then, a model was generated to see the effects of the variables towards the biobutanol produced. Furthermore, the software suggested optimum value for each parameter as temperature 49.35°C, yeast extract 1.80 g/L, and pH 4 with a biobutanol concentration of 0.405 g/L. A laboratory experiment was conducted to test the predicted variables and eventually 0.417 g/L of biobutanol concentrations was achieved, which is slightly higher than the predicted values. Moreover, growth kinetics of the bacteria towards both solvents (biobutanol, acetone, and ethanol) and acids (acetic acid and butyric acid) production under the optimized conditions was conducted and found acetic acid with the highest yield (Y p/s) value of 15.26 g/g with maximum productivity of 0.23g/L/h, while biobutanol has the lowest yield (Y p/s) value of 1.29 g/g with maximum productivity of 0.01g/L/h. The specific growth rate (µ) and doubling time (td) were found as 0.021h-1 and 33h respectively. The research concluded that Central Composite Design (CCD) is a handy and promising approach for variable optimization towards biobutanol production. However, due to the kinetics evaluated results, the bacterial strain is not apposite for biobutanol production. Nevertheless, it could be used for acetic acid production.