A novel approach to produce glucose from the supernatant obtained upon the dilute acid pre-treatment of rice straw and synergistic action of hydrolytic enzymes producing microbes

Abstract

The present work refers to a process involving the use of dilute nitric acid pretreatment and enzymatic hydrolysis for the transformation of rice straw into simple sugars. Acid pre-treated rice straw was separated into the pulp and supernatant through centrifugation and filtration. The two fractions are then converted into simple sugars by combined action of microbes producing cellulase and laccase enzymes. These microbes were isolated from soil samples which were collected from different locations with varying altitudes, expected to harbour microbes with high-hydrolysing activity. The nitric acid pretreatment was carried out at 30 °C, 200 rpm for 72 h. After 72 h, the culture supernatants were analysed for the presence of glucose with the help of HPLC. The supernatant fraction separated after the acid pre-treated rice straw produced highest amount of glucose (205 mg/g of rice straw) upon subsequent hydrolysis with synergistic action of cellulase and laccase-producing microbes.

Insight into pathway of monosaccharide production from integrated enzymatic hydrolysis of rice straw waste as feed stock for anaerobic digestion

“…74 °C, sample temp. 70 °C, 350 psi, 20 min Enzymatic hydrolysis, 50ºC, 15 min – 72 h AFEX-pretreated rice straw gave higher carbohydrates conversion Xylose was a significant part (69–70%) followed by arabinose and glucose (20–24%) for AFEX Vlasenko et al 32 Cellucalast 1.5L Novozym 188 Acid pre-treatment, 160-180ºC followed by enzymatic hydrolysis, 50ºC, 72 h Glucose and xylose release about 83% of the sugar content in the raw material Hsu et al 14 Cellulase enzyme from Genencor International, UAS Dilute H 2 SO 4 , 20 min followed by enzymatic hydrolysis, 50ºC, 60 h Total yield of glucose was about 76% of glucose in the raw material Wei et al 33 Cellic Ctec Accelerase 1000TM Accelerase 1500 TM H 2 SO 4 , 121ºC, 15 min followed by enzymatic hydrolysis, 50ºC, 72 h The highest sugar and ethanol production was found from the using of Cellic Ctec cellulase Srinorakutara et al 34 Cellulase and laccase enzyme produced from microbial culture Nitric acid pre-treatment, 160-180ºC followed by microbial degradation at 30ºC, 72 h An increase in glucose amount in the supernatant was 29.13% as compared to the control samples Chownk et al 35 Cocktails of immobilized enzymes (Celluclast 1.5L, BGL, and laccase) Dilute sulfuric acid pre-treatment, 121 ºC followed by immobilized enzymatic hydrolysis, 35-55ºC, 48 h Sugar yields were in the range of 53–67% with acid concentration from 0.1% to 1.0% H2SO4 Kumar et al 36 Cellulase enzyme from Aspergillus Niger Atres Zymix Plus (Atres group, Germany) Different integrated enzyme hydrolysis approaches: Dilute H 2 SO 4 , room temp, 4 h Dilute NaOH, room temp, 4 h Boiled water, 4 h Combined with Enzymatic hydrolysis, 50-55ºC, 48 h Boiled rice straw followed by enzymatic hydrolysis gave the highest monosaccharide yield in the digestate Glucose was the significant part (78–86%) of the monosaccharides This study …”