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<p>In this study, cellulose-degrading bacteria were isolated and screened from decayed straw by Congo red staining and filter paper strip disintegration methods before the strains were identified by morphological observation and molecular biology techniques. Carboxymethyl cellulose (CMC) activity was used as a screening index to construct a composite bacterial system. The enzyme production conditions were optimized based on the results of a single-factor and response surface experiment, and the effects of pretreatment of the composite bacterial system on the anaerobic digestion (AD) performance of hulless barley straw were evaluated. Five bacterial strains with high CMC activity were screened and used for compounding, among which three bacterial strains, <i>Bacillus velezensis</i>, <i>Bacillus licheniformis</i>, and <i>Bacillus pumilus</i> were combined to form the optimal composite bacterial system termed CS. The optimal CS enzymatic production conditions were determined to be an initial pH of 5.2, a fermentation temperature of 40.0&#xa0;°C, and a fermentation time of 70.0&#xa0;h. Under these optimized conditions, the CMC activity of CS reached 114.38 U/mL. The CS degraded lignocellulose of hulless barley straw to different degrees, and degraded hemicellulose and cellulose more effectively, with degradation rates of 8.08–38.42% and 7.45–38.06%, respectively. In addition, hulless barley straw pretreatment with CS could significantly increase methane production (<i>P</i> &lt; 0.05), with the highest cumulative methane production of 242.94&#xa0;mL/g volatile solids (VS) obtained on the 5th day of treatment, which was 55.34% higher than that of the control and comparable to that of pretreatment with chemicals. The results show that CS pretreatment is an effective method of improving the performance of methane production by AD of hulless barley straw.</p>

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Optimization of the construction of a cellulose-degrading composite bacterial system and its effect on the anaerobic digestion of hulless barley straw

  • 期刊论文

  • 发表日期：

    2025年8月23日

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  • Jinbo Yang,
  • Yi Li,
  • Zhongping Du,
  • Derui Zhu,
  • Rui Han

摘要

In this study, cellulose-degrading bacteria were isolated and screened from decayed straw by Congo red staining and filter paper strip disintegration methods before the strains were identified by morphological observation and molecular biology techniques. Carboxymethyl cellulose (CMC) activity was used as a screening index to construct a composite bacterial system. The enzyme production conditions were optimized based on the results of a single-factor and response surface experiment, and the effects of pretreatment of the composite bacterial system on the anaerobic digestion (AD) performance of hulless barley straw were evaluated. Five bacterial strains with high CMC activity were screened and used for compounding, among which three bacterial strains, Bacillus velezensis, Bacillus licheniformis, and Bacillus pumilus were combined to form the optimal composite bacterial system termed CS. The optimal CS enzymatic production conditions were determined to be an initial pH of 5.2, a fermentation temperature of 40.0 °C, and a fermentation time of 70.0 h. Under these optimized conditions, the CMC activity of CS reached 114.38 U/mL. The CS degraded lignocellulose of hulless barley straw to different degrees, and degraded hemicellulose and cellulose more effectively, with degradation rates of 8.08–38.42% and 7.45–38.06%, respectively. In addition, hulless barley straw pretreatment with CS could significantly increase methane production (P < 0.05), with the highest cumulative methane production of 242.94 mL/g volatile solids (VS) obtained on the 5th day of treatment, which was 55.34% higher than that of the control and comparable to that of pretreatment with chemicals. The results show that CS pretreatment is an effective method of improving the performance of methane production by AD of hulless barley straw.