Enzymatic Hydrolysis of Pretreated Kenaf using a Recombinant Xylanase: Effects of Reaction Conditions for Optimum Hemicellulose Hydrolysis

Nur Izyan Wan Azelee,Ahmad Fauzi Ismail,Nazlee Faisal Ghazali,Jamaliah Md Jahim,Siti Fatimah Zaharah Mohamad Fuzi,Roshanida A Rahman,Rosli Md Illias

doi:10.3844/ajabssp.2016.54.66

Nur Izyan Wan Azelee, Ahmad Fauzi Ismail + Show 5 more

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https://doi.org/10.3844/ajabssp.2016.54.66

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Abstract

An efficient hemicellulose hydrolysis has now become a crucial step for xylooligosaccharides production for food additives and nutraceuticals industries. In this study, xylanase hydrolysis of pretreated hemicellulosic kenaf (Hibiscus cannabinus) for substantial hemicellulose hydrolysis was demonstrated. Experiments were performed primarily to investigate the effect of several critical reaction conditions towards the enzymatic hydrolysis of the pre-treated kenaf. The effects of various ranges of reaction conditions (substrate loading, xylanase loading, pH, temperature and time) were systematically and thoroughly studied. The study of hemicellulosic kenaf conversion using single enzyme was proven to effectively yield up to 59% of conversion after 48 h incubation using 3% (w/v) of substrate loading and 400 U of xylanase loading at 50°C in pH 4.0 buffer systems. The use of a single xylanase on the pre-treated kenaf was a key parameter in understanding the action of the main hemicellulose degrading enzyme towards hydrolysing the hemicellulose backbone of the pre-treated kenaf. Enzyme feeding strategy was also conducted and the results revealed that a batch feeding strategy of 400 U xylanase loading yielded the highest hemicellulose hydrolysis compared to the other fed batch enzyme feeding strategy. It was concluded that each reaction conditions and enzyme feeding strategy gave a significant impact towards the enzymatic hydrolysis and the use of optimum reaction conditions resulted in a high product yield at the end of the reaction. With the discovery of the importance of each reaction conditions involved in a hydrolysis, this study highlights the need for a comprehensive investigation on the reaction conditions using a mixture of enzymes towards achieving a complete hydrolysis with a higher product yield.

Highlights

Lignocellulosic biomass is the non-starch, fibrous part of a plant material which is useful for its renewability and abundance (Otieno and Ahring, 2012a)
The high content of hemicellulose in kenaf gives an advantage for the production of high xylose and xylooligosaccharides
These chemical compositions may vary for different lignocelluloses depending on the genetics, growth environment and age of the plant, the harvest method of the biomass as well as the storage conditions of the raw material (Hames et al, 2003; Wan Azelee et al, 2014)

Summary

Introduction

Lignocellulosic biomass is the non-starch, fibrous part of a plant material which is useful for its renewability and abundance (Otieno and Ahring, 2012a). It is considered the most promising feedstock for producing biofuels and other biochemical due to its versatility, availability and low. The cellulose and hemicellulose are both polymers built up by long chains of sugar units, which (after pretreatment and hydrolysis) can be converted into intermediate products. The majority of the previous studies on hydrolysis of lignocellulosic biomass have focused on the cellulose (Ninomiya et al, 2012; Tippkötter et al, 2014; Ying et al, 2014). A few of them performed their study on the hemicellulose (Qiu et al, 2012) and this will be the main focus of this study

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