Enzymatic hydrolysis of biologically pretreated sorghum husk for bioethanol production

Document Type: Research Paper

Authors

1 Department of Biochemistry, Shivaji University, Vidyanagar, Kolhapur 416004, Maharashtra, India.

2 State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, Shandong, China.

3 Amity Institute of Biotechnology, Amity University, Mumbai, India 410206.

4 Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, South Korea.

Abstract

Biological pretreatment of lignocellulosic biomass is considered to be energy-efficient and cost-effective. In the present study, sorghum husk was biologically pretreated with a white-rot fungus Phanerochaete chrysosporium (MTCC 4955) under submerged static condition. Ligninolytic enzymes like lignin peroxidase (0.843 U/mL) and manganese peroxidase (0.389 U/mL) played an important role in the biological pretreatment of sorghum husk. Activities of different hydrolytic enzymes such as endoglucanase (57.25 U/mL), exoglucanase (4.76 U/mL), filter paperase (0.580 U/mL), glucoamylase (153.38 U/mL), and xylanase (88.14 U/mL) during biological pretreatment of sorghum husk by P. chrysosporium were evaluated. Enzymatic hydrolysis of untreated sorghum husk and biologically pretreated sorghum husk produced 20.07 and 103.0 mg/g reducing sugars, respectively. This result showed a significant increase in reducing sugar production in the biologically pretreated sorghum husk as compared to its untreated counterpart. Biologically pretreated sorghum husk hydrolysate was further fermented for 48 h using Saccharomyces cerevisiae (KCTC 7296), Pachysolen tannophilus (MTCC 1077), and their co-culture resulting in ethanol yields of 2.113, 1.095, and 2.348%, respectively. The surface characteristics of the substrate were evaluated after the delignification and hydrolysis, using FTIR, XRD, and SEM, confirming the effectiveness of the biological pretreatment process.

Graphical Abstract

Enzymatic hydrolysis of biologically pretreated sorghum husk for bioethanol production

Highlights

  • Biological pretreatment of sorghum husk using Phanerochaete chrysosporium was investigated.
  • Activities of different ligninolytic and hydrolytic enzymes during biological pretreatment were evaluated.
  • Significant increase in reducing sugar production as a result of biological pretreatment of sorghum husk vs. untreated biomass.
  • Biological pretreatment led to substantial surface morphological changes.

Keywords


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