The Preliminary Study Of Fuel Ethanol Production From Bingtang Sweet Orange Residue

Using cellulose material to produce ethanol has become the hotspot of study and application in last decades around the world. In this paper, the production of ethanol using Bingtang sweet orange residue as raw material was studied.In the production of fuel ethanol, strain is a key factor to determine the fermentation performance. Nine yeast strains were isolated from local wine yeast. Their physiological and biochemical characteristics, high-temperature endurance and high-alcoholicity endurance were compared. Results showed that remarkable differences were observed among the nine yeast strains. Among of which, Y-4 was suggested to be the optimal strain, based on the fact that it had a good utilization of sugar, that it could assimilate multiple sugar sources including xylose. In addition, Y-4 was capable of growing at 42℃, and was able to endurance 14 % (v/v) alcoholic strength. This yeast was proved to be a Pichia anomala after molecule identification.The technology of sulfuric acid hydrolysis on the Bingtang sweet orange residue was studied in this paper. Results showed that the optimum conditions for the single factor experiments were as follows: temperature 120°C; time 60 min; sulfuric acid concentration 0.15 mol/L; liquid-solid ratio 10:1. Then a L9(3~4) orthogonal experiment was designed based on the forgoing results. The results showed the optimum hydrolysis conditions were 0.15 mol/L of sulfuric acid concentration; 10:1 of liquid-solid ratio; 120°C of temperature; 90 min of time. Under these conditions, the yield of reducing sugar was 50.25%, and the weight loss of the material was 82.9%.The enzyme hydrolysis of Bingtang sweet orange residue was investigated in this paper. The influential factors of enzyme hydrolysis were studied including enzyme dosage, buffer solution type, substrate concentration, pH, reaction time and additives variety. Results showed that the optimum enzyme hydrolysis conditions were as follows: cellulase dosage 3 mg/g substrate, pectinase dosage 5 mg/g substrate, phosphoric- citric acid of the optimum buffer solution, substrate concentration 20 g/L, reaction time 48 h, Tween 80 of the best additive, and the optimum concentration of the Tween 80 was 0.5%. Under these conditions, the yield of reducing sugar was up to 61.45%, much higher than the sugar obtained in acid hydrolysis.Finally, the fermentation technology conditions of using Bingtang sweet orange residue to produce ethanol were investigated. Results showed that the optimum conditions for the single factor experiments were as follows: inoculum 12%; fermentation time 72 h; pH 4.5; fermentation temperature 33°C. Then a L9(3~4) orthogonal experiment was designed based on the forgoing results. The results showed the optimum fermentation conditions were 12% of inoculum; 72 h of fermentation time; 4.8 of pH; 33°C of fermentation temperature. Under these optimal conditions, 0.1128 g/g of ethanol yield was obtained.The study of ethanol fermentation from Bingtang sweet orange residue can be used as a theoretical basis for disposing orange peel residue. It could also play a significant guidence role in improving the economic value of citrus processing waste.