酸碱调控及底物浓度对木糖发酵产酸特性的影响

以木糖为碳源采用间歇培养方式,对木糖厌氧发酵产酸进行研究。考察木糖浓度和初始pH值对木糖厌氧产酸的影响。结果表明,随着木糖浓度的增加,总产酸量得到提高,但木糖利用率却呈现下降的趋势。当木糖浓度为5 g/L时,其利用率为100%,15 g/L时利用率为73.9%,此时挥发性脂肪酸(VFAs)为9.22 g/L。木糖的分批投加可有效促进产酸,尤其是促进乙酸浓度的提高。pH为5.0和6.0左右时,VFAs主要成分为乙酸和丁酸;而pH为7.0～9.0时,乙酸含量明显增高,在pH值为8.0的条件下乙酸含量占总VFAs的80.1%。在pH=8.0时经过8 d左右的发酵,VFAs浓度可达9.34 g/L。

Effect of xylose concentrations and pH on acid fermentation from xylose by activated sludge

Lignocellulose is a major component of crop straw, and xylose is an important monosaccharide among the hydrolyzates of Lignocellulose. Using xylose as carbon source, the acid fermentation under the anaerobic condition was studied with the batch fermentation. The effects of xylose concentration and initial pH on the conversion of xylose to VFAs were studied. The results showed that with the increasing concentration of xylose, the total amount of acid production was improved, but the xylose utilization showed a downward trend. At the xylose concentration of 5 g/L, its utilization was 100%. At 15 g/L, the utilization was 73.9% and VFAs reached to 9.22 g/L. When pH was 5.0 and 6.0 or so, VFAs mainly composed of acetate and butyrate; and when pH was 7.0 to 9.0, acetate concentration significantly increased. At pH 8.0, acetate counted 80.1% of total VFAs, and VFAs concentration reached up to 9.34 g/L.