DOI: https://doi.org/10.55373/mjchem.v24i2.88

Keywords: Rice straw; solid state fermentation; total phenolic content; antioxidant activity

Abstract

Rice straw is an agricultural waste material that is abundantly available in Malaysia. Field burning is the main method used for eliminating rice straw, but this increases air pollution and consequently affects public health. In this study, rice straw was utilized as a substrate for solid state fermentation (SSF) using Aspergillus oryzae. SSF was conducted at 30 °C, with 70 % initial moisture content and 10 % v/v of inoculum level. The effects of fermentation duration on the total phenolic content, total flavonoid content and antioxidant activity were investigated. It was found that solid state fermentation enhanced the extractability of the total phenolic content by 104.4 % and the total flavonoid content by 5.32 % after ten days. The antioxidant activity of rice straw increased as fermentation progressed, with an increase of 90.01 % in DPPH radical scavenging activity and 89.24% in the FRAP value. The activity of xylanase and β-glucosidase enzymes produced during SSF was also investigated to study the relationship between polyphenols and the antioxidant activity of fermented rice straw extracts. Both enzymes showed an increase in activity as fermentation progressed proving that the enzymes played a significant role in releasing bound phenolics during SSF.