Enhancement of seaweed bioavailability for phenol production through fermentation process using Aspergillus oryzae / Norakma Mohd Nor

Edible seaweeds are a good source of antioxidants, dietary fibers, essential amino acids, vitamins, phytochemical and minerals. Phenolic compounds are usually extracted using hot water and organic solvent extraction. The disadvantage of these techniques is its low yield of bound phenolics. The ability of microbial fermentation to improve the yield and change the phenolic profiles was mainly due to the release of bound phenolic compounds by microbial enzymes produced during fermentation. The specific objectives of this study were to screen the fermentation method for better total
phenolic content (TPC) production, to optimize the parameters (inoculum level, initial moisture content, temperature and fermentation days) during fermentation through Response Surface Methodology (RSM), to investigate the relationship between TPC and antioxidant activity with enzymes produced during fermentation, to study the effects of fermentation on the profiling, antimicrobial activity and characteristics of fermented seaweed extracts obtained and to determine the antioxidant activity, physico-chemical and sensory characteristics of chilli sauce incorporated with fermented seaweed extract. Results obtained indicated that solid state fermentation (SSF) was able to extract the highest TPC compared to submerged fermentation (SmF). The optimum SSF conditions using RSM was found at 4 days, 30 °C, 70% initial moisture content and 10% (v/v) inoculum level, respectively with desirability value 0.979. TPC, DPPH radical scavenging activity, total flavonoid content (TFC) and ferric-reducing antioxidant power (FRAP) showed positive correlation with cellulase, β-glucosidase and xylanase activity at p < 0.05. Total amino acid was also increased after SSF. However, phenolics profiles and volatile compounds showed some compounds were increased while some other compounds were decreased by
SSF. Caffeic acid was found to present in all samples and also enhanced through SSF. The TPC and antioxidant activity of chilli sauce incorporated with fermented seaweed extracts were enhanced compared to raw fermented seaweed extracts and were superior compared to control chilli sauce. Physico-chemical characterisation of chilli sauce incorporated with fermented seaweed extracts showed that there was no serum separation observed after two months of storage. The results suggested that chilli sauce incorporated with fermented seaweed extract could be an alternative choice to corn starch in high acid foods. Therefore, the application of SSF in the seaweed processing industry can contribute to the development of value-added food ingredients with enhanced bioactivity.