van der Pol Edwin C, Eggink Gerrit, Weusthuis Ruud A
Bioprocess Engineering, Wageningen University and Research, PO Box 16, 6700 AA Wageningen, The Netherlands ; Food and Biobased Research, Wageningen University and Research, PO Box 17, 6700 AA Wageningen, The Netherlands.
Bioprocess Engineering, Wageningen University and Research, PO Box 16, 6700 AA Wageningen, The Netherlands.
Biotechnol Biofuels. 2016 Nov 15;9:248. doi: 10.1186/s13068-016-0646-3. eCollection 2016.
Sugars derived from lignocellulose-rich sugarcane bagasse can be used as feedstock for production of l(+)-lactic acid, a precursor for renewable bioplastics. In our research, acid-pretreated bagasse was hydrolysed with the enzyme cocktail GC220 and fermented by the moderate thermophilic bacterium DSM2314. Saccharification and fermentation were performed simultaneously (SSF), adding acid-pretreated bagasse either in one batch or in two stages. SSF was performed at low enzyme dosages of 10.5-15.8 FPU/g DW bagasse.
The first batch SSF resulted in an average productivity of 0.78 g/l/h, which is not sufficient to compete with lactic acid production processes using high-grade sugars. Addition of 1 g/l furfural to precultures can increase resistance towards by-products present in pretreated lignocellulose. Using furfural-containing precultures, productivity increased to 0.92 g/l/h, with a total lactic acid production of 91.7 g in a 1-l reactor containing 20% W/W DW bagasse. To increase sugar concentrations, bagasse was solubilized with a liquid fraction, obtained directly after acid pretreatment. Solubilizing the bagasse fibres with water increased the average productivity to 1.14 g/l/h, with a total lactic acid production of 84.2 g in a 1-l reactor. Addition of bagasse in two stages reduced viscosity during SSF, resulting in an average productivity in the first 23 h of 2.54 g/l/h, similar to productivities obtained in fermentations using high-grade sugars. Due to fast accumulation of lactic acid, enzyme activity was repressed during two-stage SSF, resulting in a decrease in productivity and a slightly lower total lactic acid production of 75.6 g.
In this study, it is shown that an adequate production of lactic acid from lignocellulose was successfully accomplished by a two-stage SSF process, which combines acid-pretreated bagasse, precultivated in the presence of furfural as microorganism, and GC220 as enzyme cocktail. The process may be further improved by enhancing enzyme hydrolysis activities at high lactic acid concentrations.
源自富含木质纤维素的甘蔗渣的糖类可作为生产可再生生物塑料的前体l(+)-乳酸的原料。在我们的研究中，酸预处理的甘蔗渣用酶混合物GC220进行水解，并由嗜热适中的细菌DSM2314进行发酵。糖化和发酵同时进行（同步糖化发酵，SSF），将酸预处理的甘蔗渣分一批或分两个阶段添加。同步糖化发酵在低酶剂量10.5 - 15.8 FPU/g干重甘蔗渣的条件下进行。
第一批同步糖化发酵的平均产率为0.78 g/(l·h)，这不足以与使用优质糖的乳酸生产工艺竞争。向预培养物中添加1 g/l糠醛可提高对预处理木质纤维素中存在的副产物的抗性。使用含糠醛的预培养物时，产率提高到0.92 g/(l·h)，在含有20%（重量/重量）干重甘蔗渣的1升反应器中，乳酸总产量为91.7 g。为了提高糖浓度，甘蔗渣用酸预处理后直接获得的液体部分进行溶解。用水溶解甘蔗渣纤维使平均产率提高到1.14 g/(l·h)，在1升反应器中乳酸总产量为84.2 g。分两个阶段添加甘蔗渣降低了同步糖化发酵过程中的粘度，在前23小时的平均产率为2.54 g/(l·h)，类似于使用优质糖进行发酵所获得的产率。由于乳酸的快速积累，在两阶段同步糖化发酵过程中酶活性受到抑制，导致产率下降，乳酸总产量略低，为75.6 g。
在本研究中，表明通过两阶段同步糖化发酵工艺成功实现了从木质纤维素中充分生产乳酸，该工艺将在糠醛存在下预培养的酸预处理甘蔗渣作为微生物，以及GC220作为酶混合物。通过提高高乳酸浓度下的酶水解活性，该工艺可能会得到进一步改进。
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