Evaluation of pre-treatment methods for Lantana camara stem for enhanced enzymatic saccharification

This study evaluates certain pre-treatment methods for Lantana camara stem for efficient conversion to fermentable sugars. The composition analysis of L. camara stem showed 66.8% (w/w) holocellulose, 34.9% (w/w) cellulose and 17% (w/w) hemicellulose. Comparative analysis of various chemical, physical or physico-chemical pre-treatments on L. camara stem was performed. Of all pretreatment methods used, pre-treatment with 1% (v/v) H₂SO₄ assisted autoclaving gave maximum total reducing sugar yield 132.7 mg/g (13.2 g/L) of raw biomass in pretreated hydrolysate. Major contribution to total reducing sugar was from hemicellulosic fraction, because total pentose sugar yield was 119.4 mg/g of raw biomass whereas, glucose released was only 10 mg/g of untreated biomass. The enzymatic saccharification of pre-treated L. camara stem by 1% (v/v) H₂SO₄ assisted autoclaving was performed with partially purified carboxymethylcellulase from Bacillus amyloliquefaciens SS35. Enzymatic saccharification at 30 °C for 48 h gave total reducing sugar yield, 63.3 mg/g of pre-treated biomass in the hydrolysate, while untreated biomass gave 43.3 mg/g of untreated biomass. The total sugar yield i.e. the sum of pre-treated biomass hydrolysate total reducing sugar (132.7 mg/g of raw biomass) and enzymatic hydrolysate total reducing sugar (63.3 mg/g of pre-treated biomass) was 196.0 mg/g of raw biomass, indicating the effectiveness of pre-treatment method. Field emission scanning electron microscopy, Fourier transform infrared and X-ray diffraction analyses displayed enhanced porosity, removal of non-cellulosic sugars and increased cellulose crystallinity, respectively, in pre-treated L. camara stem, showing the effectiveness of acid assisted autoclaving pre-treatment.