Pretreatment of oil palm residues by dilute alkali for cellulosic ethanol production / 生物工程学报

In the study, we used oil palm residues (empty fruit bunch, EFB) as raw material to produce cellulosic ethanol by pretreatment, enzymatic hydrolysis and fermentation. Firstly, the pretreatment of EFB with alkali, alkali/hydrogen peroxide and the effects on the components and enzymatic hydrolysis of cellulose were studied. The results show that dilute alkali was the suitable pretreatment method and the conditions were first to soak the substrate with 1% sodium hydroxide with a solid-liquid ratio of 1:10 at 40 degrees C for 24 h, and then subjected to 121 degrees C for 30 min. Under the conditions, EFB solid recovery was 74.09%, and glucan, xylan and lignin content were 44.08%, 25.74% and 13.89%, respectively. After separated with alkali solution, the pretreated EFB was washed and hydrolyzed for 72 h with 5% substrate concentration and 30 FPU/g dry mass (DM) enzyme loading, and the conversion of glucan and xylan reached 84.44% and 89.28%, respectively. We further investigated the effects of substrate concentration and enzyme loading on enzymatic hydrolysis and ethanol batch simultaneous saccharification and fermentation (SSF). The results show that when enzyme loading was 30 FPU/g DM and substrate concentration was increased from 5% to 25%, ethanol concentration were 9.76 g/L and 35.25 g/L after 72 h fermentation with Saccharomyces cerevisiae (inoculum size 5%, V/V), which was 79.09% and 56.96% of ethanol theory yield.

Stability of whole cell biocatalyst for biodiesel production from renewable oils / 生物工程学报

Lipase-mediated biodiesel production becomes increasingly important because of mild reaction conditions, pollution free during the process and easy product separation. Compared with traditional immobilized lipase, whole cell biocatalyst is promising for biodiesel production because it is easy to prepare and has higher enzyme activity recovery. Rhizopus oryzae IFO4697 can be used as the catalyst for biodiesel production. To further study the stability of the whole cell biocatalyst is extremely important for its further application on large scale. This paper focuses on the stability study of Rhizopus oryzae IFO4697 when used for the methanolysis of renewable oils for biodiesel production. The results showed that water content was important for achieving high catalytic activity and good stability of the biocatalyst. The optimum water content was found to be 5%-15%. Both particle size and desiccation methods showed no obvious effect on the stability of the biocatalyst. With GA cross-linking pretreatment, the stability of the biocatalyst could be improved significantly. When Rhizopus oryzae IFO4697 repeatedly used for next batch reaction, direct vacuum filtration was found to be a good way for the maintenance of good stability of the biocatalyst. Under the optimum reaction conditions, the methyl ester yield could keep over 80% during 20 repeated reaction batches.