Commercial and non-commercial pectinase and cellulase on the enzymatic hydrolysis efficacy of rice husk and Tifton 85 hay

ABSTRACT. The aim of this study was to evaluate the action of commercial and non-commercial cellulase and pectinase on rice husk and Tifton 85 hay hydrolyses. The hydrolysis kinetics of the substrates with commercial cellulase and pectinase were evaluated and the hydrolysis at different temperature and agitation conditions was maximized using experimental design. The combined use of commercial and non-commercial enzymes under optimized conditions was evaluated. The pre-treatment of the residues was also investigated by milling and different concentrations of NaOH. Finally, the effect of the hydrolysis on the bromatological composition of the residues was evaluated. The best hydrolysis times of rice husk and Tifton 85 hay were 10 and 12h for commercial cellulase, 12 and 14h for non-commercial cellulase, 10 and 14h for commercial pectinase and 16 and 20h for non-commercial pectinase, respectively. The highest hydrolysis values were obtained using commercial cellulase with 1:50 (w:v enzyme:water) dilution rate, at 45ºC and 300 rpm agitation for both substrates, reaching 20.6% maximum percentage for Tifton 85 hay and 11.6% for rice husk. The combined use of commercial enzymes did not increase hydrolysis percentage. The pre-treatment using 7.5% NaOH and 0.5 mm grain size significantly increased the rice husk and Tifton 85 hay hydrolyses (60-80%), either using commercial cellulase or pectinase enzymes. The use of non-commercial enzymes provided 18-30% hydrolysis obtained from commercial ones. Bromatological analyzes indicated a reduction in neutral detergent fiber and acid detergent fiber content for rice husk and Tifton 85 hay when using pectinases and commercial cellulases.

摘要。本研究旨在评估商用与非商用纤维素酶（cellulase）、果胶酶（pectinase）对稻壳及Tifton 85干草水解反应的作用效果。首先，本研究评估了商用纤维素酶与果胶酶作用于底物的水解动力学特性，并通过实验设计优化了不同温度、搅拌条件下的水解反应参数；同时探究了优化条件下商用与非商用酶复配使用的效果。此外，本研究还通过研磨处理与不同浓度氢氧化钠（NaOH）溶液对原料残渣进行预处理，并评估了水解反应对残渣营养组成的影响。实验结果表明：针对商用纤维素酶，稻壳与Tifton 85干草的最优水解时长分别为10h与12h；非商用纤维素酶对应的最优时长则为12h与14h；商用果胶酶的最优水解时长为10h与14h，非商用果胶酶则为16h与20h。当使用1:50（质量体积比，酶:水）稀释的商用纤维素酶，在45℃、300转每分钟（rpm）搅拌条件下处理两种底物时，可获得最高水解率：Tifton 85干草的最大水解率达20.6%，稻壳为11.6%。复配商用酶并未提升水解率。采用7.5%氢氧化钠溶液处理且研磨至0.5mm粒径的预处理方式，无论搭配商用纤维素酶还是果胶酶，均可使稻壳与Tifton 85干草的水解率显著提升至60%~80%。非商用酶的水解效果仅为商用酶的18%~30%。营养成分分析结果显示，使用果胶酶与商用纤维素酶处理后，稻壳与Tifton 85干草的中性洗涤纤维与酸性洗涤纤维含量均有所降低。