No abstract

Rhodopseudomonas palustris TN1 was isolated from Songkhla Lake, Thailand. It phototrophically generates H(2) from the predominant volatile fatty acids (VFAs) produced from microbial dark-fermentations of palm oil milling effluent; yields from 20 mM butyrate, acetate and propionate were 4.7, 2.5, and 1.7 mol H(2) mol VFA(-1) with light efficiencies of 1.8, 1, and 0.2%, respectively. Optimum conditions were pH 7 and 3000 lux, although production was reduced by only 33% at 1000 lux. CO(2) evolution never exceeded 9 mmol mol VFA(-1).

Palm pressed fiber (PPF) is a clean and renewable lignocellulosic material. The PPF and delignified PPF (DPPF) were used as a carrier for immobilization of Candida shehatae TISTR5843 in bioethanol production. PPF was pre-treated by milling to obtain small particles, whereas DPPF was the delignification of PPF using NaClO2. C. shehatae TISTR5843 was grown in modified yeast extractmalt (YM) medium at 30 ± 2ºC on an orbital shaker at 150 rpm for batch and repeated batch fermentation. In the batch system, immobilized cells on a small size, less than 0.5 mm, of DPPF (sDPPF) gave the maximum ethanol production of 11.5 g L -1 at 24 hrs cultivation period. The ethanol concentration and ethanol yield of sDPPF were 6.2% and 6.8% higher (ethanol production 11.5 g L -1 , ethanol yield 0.47 g g -1 ) than those of free cells (ethanol production 10.8 g L -1 , ethanol yield 0.44 g g -1 ) after 36 hrs of cultivation. In contrast, the small size of PPF (sPPF) was selected as a carrier in repeated batch fermentation for cost effectiveness. The ethanol productivity of immobilized yeast cells in repeated batch fermentations was 45.2-51.6% greater than that obtained from batch fermentations. The immobilized cells on sPPF improved the ethanol production and could be reused 4 times with retaining the activity of 93%. In conclusion, PPF is a potential carrier in the immobilization system. The pre-treatment of PPF increases the surface area that enhances cell adsorption and ethanol production by C. shehatae TISTR5843.

No abstract