Department of Chemistry and Chemical Engineering, Beijing Forestry University, Beijing, China.
Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00, Lund, Sweden.
Biotechnol Biofuels. 2011 Jul 31;4:22. doi: 10.1186/1754-6834-4-22.
As the supply of starch grain and sugar cane, currently the main feedstocks for bioethanol production, become limited, lignocelluloses will be sought as alternative materials for bioethanol production. Production of cellulosic ethanol is still cost-inefficient because of the low final ethanol concentration and the addition of nutrients. We report the use of simultaneous saccharification and cofermentation (SSCF) of lignocellulosic residues from commercial furfural production (furfural residue, FR) and corn kernels to compare different nutritional media. The final ethanol concentration, yield, number of live yeast cells, and yeast-cell death ratio were investigated to evaluate the effectiveness of integrating cellulosic and starch ethanol.
Both the ethanol yield and number of live yeast cells increased with increasing corn-kernel concentration, whereas the yeast-cell death ratio decreased in SSCF of FR and corn kernels. An ethanol concentration of 73.1 g/L at 120 h, which corresponded to a 101.1% ethanol yield based on FR cellulose and corn starch, was obtained in SSCF of 7.5% FR and 14.5% corn kernels with mineral-salt medium. SSCF could simultaneously convert cellulose into ethanol from both corn kernels and FR, and SSCF ethanol yield was similar between the organic and mineral-salt media.
Starch ethanol promotes cellulosic ethanol by providing important nutrients for fermentative organisms, and in turn cellulosic ethanol promotes starch ethanol by providing cellulosic enzymes that convert the cellulosic polysaccharides in starch materials into additional ethanol. It is feasible to produce ethanol in SSCF of FR and corn kernels with mineral-salt medium. It would be cost-efficient to produce ethanol in SSCF of high concentrations of water-insoluble solids of lignocellulosic materials and corn kernels. Compared with prehydrolysis and fed-batch strategy using lignocellulosic materials, addition of starch hydrolysates to cellulosic ethanol production is a more suitable method to improve the final ethanol concentration.
随着淀粉颗粒和甘蔗作为生物乙醇生产的主要原料供应变得有限，木质纤维素将被寻求作为生物乙醇生产的替代材料。由于最终乙醇浓度低和需要添加营养物质，纤维素乙醇的生产仍然成本效益不高。我们报告了使用木质纤维素残渣从商业糠醛生产（糠醛残渣，FR）和玉米粒进行同步糖化和共发酵（SSCF），以比较不同的营养介质。考察了最终乙醇浓度、产率、活酵母细胞数和酵母细胞死亡率，以评估整合纤维素和淀粉乙醇的效果。
随着玉米浓度的增加，乙醇产率和活酵母细胞数均增加，而 SSCF 中 FR 和玉米颗粒的酵母细胞死亡率降低。在 FR 纤维素和玉米淀粉的 101.1%乙醇产率基础上，在 7.5% FR 和 14.5%玉米颗粒的矿盐培养基中，SSCF 在 120 小时时获得了 73.1g/L 的乙醇浓度。SSCF 可以从 FR 和玉米颗粒同时将纤维素转化为乙醇，并且有机和矿盐培养基中的 SSCF 乙醇产率相似。
淀粉乙醇通过为发酵生物提供重要的营养物质来促进纤维素乙醇的生产，而纤维素乙醇通过提供将淀粉材料中的纤维素多糖转化为额外乙醇的纤维素酶来促进淀粉乙醇的生产。使用矿盐培养基在 FR 和玉米颗粒的 SSCF 中生产乙醇是可行的。在高浓度不溶性固体的木质纤维素材料和玉米颗粒的 SSCF 中生产乙醇将具有成本效益。与使用木质纤维素材料的预处理和分批补料策略相比，将淀粉水解物添加到纤维素乙醇生产中是提高最终乙醇浓度的更合适方法。
