ISHS Acta Horticulturae 389: V International Sago Symposium
CONTINUOUS ETHANOL PRODUCTION BY ZYMOMONAS MOBILIS FROM SAGO STARCH HYDROLYSATE AND NATURAL RUBBER WASTE |
| Authors: | A. Ishizaki, S. Tripetchkul |
| Abstract:
The feasibility of using sago starch hydrolysate (enzyme saccharification) as a carbon source instead of pure glucose and natural rubber serum powder (NRSP) as a nutritional source instead of yeast extract for the medium of ethanol fermentation by Zymomonas mobilis was investigated. The results showed that sago starch hydrolyzed with amylase and NRSP either as it is or hydrolyzed with proteinase have the potential to be used as a fermentation medium resource. It was found that specific glucose uptake rate, specific ethanol production rate and ethanol yield on sago starch hydrolysate with NRSP hydrolysate-Mieki medium (10% initial glucose concentration) are comparable to those values on pure glucose-yeast extract medium. The continuous fermentation in 1 litre jar fermentor with a working volume of 500 ml at pH 5.5, 30 C, was accomplished by pH-stat with separate inflows of alkali and feed medium controlled through a digital set point control (DSC) with two pH set points; a high limit and a low limit. A small difference between the higher pH set point and a lower pH set point and a short control interval time resulted high ethanol productivity, 11.1 g/l h, with high dilution rate, 0.27 l/h. Higher ethanol productivity for Z. mobilis using the medium consisting of sago starch hydrolysate and rubber industry waste is expected if the measures to release the product inhibition is adopted. | |
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