热碱预处理对菊芋茎秆组成和酶水解影响

Effects of hot-NaOH pretreatment on Jerusalem artichoke stalk composition and subsequent enzymatic hydrolysis

摘要:

为了深入了解菊芋茎秆用于生物能源转化的潜力，在对菊芋茎秆的全秆、韧皮以及髓芯的组成分析基础上，采用不同浓度的NaOH在121 ℃对菊芋茎秆进行预处理，并对预处理后的茎秆进行酶水解。结果表明：菊芋茎秆具有较高木质素含量 (32.0%)，且韧皮中木质素含量最高；茎秆中碳水化合物总含量与传统农作物秸秆相当，但纤维素含量相对较高 (40.5%)，半纤维含量相对较低 (19.6%)。经不同浓度NaOH预处理后，相对于未处理茎秆，全秆、韧皮以及髓芯中木质素含量分别降低13.1%–13.4%、8.3%–13.5%和19.9%–27.2%，半纤维素含量分别降低了87.8%–96.9%、87.6%–95.0%和74.0%–90.2%。纤维素含量在全秆、韧皮和髓芯中相应增加了56.5%–60.2%、52.2%–55.4%和62.7%–73.2%。酶水解的结果显示，增加预处理过程中NaOH的浓度，全秆和韧皮的水解率可被提高2.3–2.6倍和10.3–18.5倍。虽然热NaOH预处理可以有效地改善髓芯水解性能，但经过高浓度的NaOH (2.0 mol/L) 预处理，髓芯的水解性能下降明显。由此可见，菊芋用于生物能源转化技术中，热碱法可较好地适用于菊芋秸秆预处理。提高碱浓度，有利于半纤维素和木质素的去除，并实现酶水解糖化产率的提高。但鉴于碱浓度过高会造成髓芯糖产率降低，热碱预处理菊芋秸秆工艺条件需进一步优化。

Abstract:

In order to explore the possibility of Jerusalem artichoke stalk for bioenergy conversion, we analyzed the main composition of whole stalk, pitch, and core of the stalk. Meanwhile, these parts were pretreated with different NaOH concentrations at 121 °C. Afterwards, enzymatic hydrolysis was performed to evaluate the pretreatment efficiency. Jerusalem artichoke stalk was characterized by relatively high lignin content (32.0%) compared with traditional crop stalks. The total carbohydrate content was close to that of crop stalks, but with higher cellulose content (40.5%) and lower hemicellulose (19.6%) than those of traditional crop stalks. After pretreatment, the lignin content in the whole stalk, pitch, and core decreased by 13.1%–13.4%, 8.3%–13.5%, and 19.9%–27.2%, respectively, compared with the unpretreated substrates. The hemicellulose content in the whole stalk, pitch, and core decreased 87.8%–96.9%, 87.6%–95.0%, and 74.0%–90.2%, respectively. Correspondingly, the cellulose content in the pretreated whole stalk, pitch, and core increased by 56.5%–60.2%, 52.2%–55.4%, and 62.7%–73.2%, respectively. Moreover, increase of NaOH concentration for pretreatment could improve the enzymatic hydrolysis of the whole stalk and pitch by 2.3–2.6 folds and 10.3–18.5 folds, respectively. The hydrolysis of pretreated stalk core decreased significantly as 2.0 mol/L NaOH was employed, although the increased NaOH concentration can also improve its hydrolysis performance. Based on these results, hot-NaOH can be regarded as an option for Jerusalem artichoke stalk pretreatment. Increasing NaOH concentration was beneficial to hemicellulose and lignin removal, and consequently improved sugar conversion. However, the potential decrease of sugar conversion of the pretreated core by higher NaOH concentration suggested further optimization on the pretreatment conditions should be performed.