Optimization of alkali pretreatment for bioconversion of poplar (Populus deltoides) biomass into fermentable sugars using response surface methodology

► Statistical experimental design was used to optimize pretreatment parameters. ► FTIR study suggests chemical deformation of the biomass during pretreatment. ► Development of crack and pores was visualized by scanning electron microscopy. In the present investigation, statistical experimental design was used to optimize pretreatment parameters such as alkali concentration, solid to liquid ratio, temperature, and time period of treatment to achieve the highest saccharification yield using poplar biomass. A maximum saccharification rate of 41.5% was obtained after optimization of the pretreatment condition. The optimal alkali treatment conditions for poplar wood were found to be 2.8% NaOH with ratio of 1:8 at 94°C for 60min. The results of a confirmation experiment under the optimum conditions agreed well with model predictions. The physicochemical changes in substrate after alkali treatment were evaluated by Fourier transmission infrared spectroscopic analysis and scanning electron microscopy. Fourier transmission infrared spectroscopic results showed that alkali treatment removed large fractions of lignin. Scanning electron micrograph revealed the pores and cracks developed during pretreatment.