Comparison of sodium hydroxide and sodium bicarbonate pretreatment methods for characteristic and enzymatic hydrolysis of sago palm bark

ABSTRACT

The present work utilized a by-product of the starch industry in Malaysia, Sago bark waste (SB), for pretreatment and enzymatic hydrolysis. SB was subjected to two types of alkaline pretreatment to assess their effect on SB characteristic, inhibitor formation, and enzymatic hydrolysis sugar yield. Dilute sodium hydroxide (DSH) and dilute sodium bicarbonate (DSB) were used for SB pretreatment. The pretreatment was carried out in a conventional heating environment (120ºC) for 10 min before the enzymatic hydrolysis step. The results showed that the treated SB by DSB resulted in higher removal of lignin (28%) compared to DSH (25%). The TGA, XRD, and SEM analysis results revealed that both types of pretreatment have slight differences. The crystallinity index (CI) for DSH and DSB was 43.2% and 41.2%, respectively. Meanwhile, HPLC results illustrated that the only inhibitor present in the pretreatment liquor is acetic acid at 0.25 mg/ml for DBS pretreatment and 0.063 mg/ml for DSH pretreatment. 229 ± 12 mg/g of total reducing sugar was found using DSH pretreatment, which is slightly higher than that one was obtained by DSB pretreatment (219 ± 16 mg/g) after enzymatic hydrolysis step. A similar observation was found on glucose and xylose yield. These results make us interfere that the diluted level of sodium bicarbonate can lead to approximately similar results of sodium hydroxide, which offer a cheap route of the pretreatment process.

KEYWORDS:

• Alkali pretreatment
• hydrolysis
• sago palm
• sodium hydroxide
• sodium bicarbonate

Acknowledgments

The authors appreciate the financial support from Universiti Putra Malaysia under the UPM-IPS research grant.

Additional information

Funding

This work was supported by the UPM-IPS research grant [UPM-IPS research grant].

Notes on contributors

Saleem Ethaib

Saleem Ethaib got his PhD from chemical & environmental engineering Department, University Putra Malaysia (UPM). He serves in University of Thi-Qar. He is a specialist in Environmental engineering and has research interest in biomass conversion, microwave-assisted processes, waste treatment, water and wastewater, solid waste management, sustainability, environmental pollution and renewable energy.

Rozita Omar

Rozita Omar got her PhD from chemical & environmental engineering Department, University Putra Malaysia (UPM). She serves in University Putra Malaysia. Her research interests are petroleum refining, bioprocess, waste and microwave treatment.

Siti Mazlina Mustapa Kamal

Dr. Siti Mazlina Mustapa Kamal got her Ph.D in Chemical Engineering from University of Manchester.). She serves in University Putra Malaysia. Her research interests are chemical engineering and food process engineering. Her current research activities  include kinetics and mechanism of subcritical hydrolysis of waste products  from bakery industry for oligosaccharides formation, pressurized water extraction (PWE) for extracting polysaccharide from freshwater microalgae, and combined model of hydrodynamics with fermentation kinetics for xylitol fermentation in bioreactor using computational fluid dynamics (CFD).

Dayang Radiah Awang Biak

Dayang Radiah Awang Biak got her PhD from Birmingham university. She serves in University Putra Malaysia. Her research interests are heat Transfer, modelling, food Processing, crystallisation, pharmaceutical products