Dilute alkaline pretreatment for reducing sugar production from Tetraselmis suecica and Chlorella sp. biomass

Abstract

Dilute alkaline pretreatment of two different types of microalgal biomass (Tetraselmis suecica and Chlorella sp.) was investigated and the pretreated biomass was subjected for enzymatic saccharification. The effect of pretreatment parameters such as alkaline concentration, temperature and reaction time on reducing sugar production from both microalgal biomass has been investigated. The maximum reducing sugar concentration from T. suecica (81mg/gdriedbiomass) was obtained when the biomass was pre-treated with 2% (w/v) of potassium hydroxide (KOH) at 120°C for 120min. While, maximum reducing sugar concentration from Chlorella sp. biomass (88mg/gdriedbiomass) was obtained when the pretreatment was carried out using 2% (w/v) sodium hydroxide (NaOH) at 120°C for 30min. Solid residue post pretreatment was analyzed using Fourier transform infrared spectroscopy and scanning electron microscopy. These analyses revealed that the functional group such as acetyl and hydroxyl groups, structure and surface of both biomass were changed through pretreatment, which is favorable for enzymatic saccharification. Enzymatic saccharification of both pretreated microalgal biomass showed 2–2.5 times higher reducing sugar concentration compared to untreated biomass. Overall, this study concluded that dilute alkaline pretreatment could be a promising alternative method replacing acid pretreatment to enhance the reducing sugar production through enzymatic saccharification of microalgal biomass.