Subcritical water hydrolysis of spent Java Citronella biomass for production of reducing sugar

The present study investigate the production of reducing sugars from spent Java citronella (Cymbopogon winterianus Jowitt) biomass using subcritical water (SCW) treatment in a batch reactor. The effect of process parameters such as temperature (140-220 °C) and reaction time (5-40 min) on total reducing sugar (TRS) yield was studied. The production of TRS increased with an increase in the temperature from 140-160 °C and decreased thereafter. The maximum amount of TRS 132.09 mg.g-1 biomass was obtained at 160°C and 30 min reaction time. The formation of sugar inhibitors (5-HMF or Furfural) was almost insignificant upto 160°C, but increased subsequently with an increase in the reaction temperature and time. The maximum inhibitors concentration of 16.70 mg.g-1 was obtained at 220°C and 30 min reaction time, which includes 5.77 mg.g-1 of 5-HMF and 10.93 mg.g-1 of furfural. The crystallinity index (CI) value of biomass sample increased from 35.30% to 52.68% with an increase in the temperature from 140-180°C, further increased in temperature to 220°C decreases the CI abruptly to 20.15% thereby altering the biomass to relatively amorphous. The porous external surface as observed in scanning electron microscopic analysis of the sample after SCW treatment showed significant removal of sugars and lignin.