Optimisation of fermentation conditions for bioethanol production from oil palm trunk sap bySaccharomyces cerevisiae

Aims: Oil palm trunk (OPT) can be a potential biomass from replanting activities for biomass-to-liquid (BTL) particularly in bioethanol production. The OPT contains higher carbohydrates compared to other oil palm biomass, thus has better advantages as feedstock for biofuel. To realise this, the feasibility of using oil palm trunk (OPT) sap as a substrate for bioethanol fermentation was explored via optimising the various culture conditions (pH, temperature, inoculum size, nitrogen source, dilution effect and growth medium) using Saccharomyces cerevisiae. Methodology and results: A total of six parameters were tested for optimising bioethanol production i.e. pH, temperature, inoculum size, nitrogen source, dilution effect and types of medium. Results showed that the optimum conditions for OPT sap in bioethanol production were at pH 4.0, temperature of 30 °C, inoculum size of 10 % (v/v), without requirement of nitrogen supplementation and substrate dilution. A fermentation period of 24 h was best for bioethanol production and resulted in bioethanol production, formation rate and yield of 47.5 g/L, 1.98 g/h and 0.50 g/g, respectively. Conclusion, significance and impact study: The study has clearly demonstrated that high efficient bioethanol production from OPT sap is possible but it is susceptible to various fermentation influencing parameters. This study could establish an effective and sustainable utilisation of waste OPT especially its sap as a lignocellulosic biomass supplement from the oil palm industry for second generation biofuel production.

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.