Study On Correlations Between Contents Of Phenolic Compounds Of Wheat Bran Fermented By Aspergillus Awamori And Activities Of Three Types Of Enzyme And Biological Activities

Wheat bran is consisted of the external layer of wheat seeds and aleurone layer. It mainly contains two kinds of physiological activators: Active polysaccharides and phenolic compounds, such as flavonoid, phenolic acids, lignan, etc. Recently, extractions of phenolic compounds from wheat brans are becoming research hotspots. However, there are only a few researches studying extractions of phenolic compounds through microorganism fermentation.In this article, solid state fermentation of wheat bran was performed by three Aspergillus awamori strains(GIM3.266, GIM3.4, GIM3.5, respectively) for 8 days consecutively. Different forms of phenolic compounds in wheat bran were extracted and analyzed on a daily basis. The activities of xylanase, cellulose and feruloyl esterase were also investigated during the fermentation process to find out their correlations. Besides, contents of different forms of phenolic compounds in wheat bran were analyzed by HPLC. Their biological properties were also investigated, such as oxidation resistance, bacteriostasis.The main research contents are listed as follows:1. Correlations between contents of phenolic compounds of unfermented and fermented wheat bran and activities of three types of enzymeSolid state fermentation of wheat bran was performed by three Aspergillus awamori strains(GIM3.266, GIM3.4, GIM3.5, respectively) for 8 days consecutively. Different forms of phenolic compounds in wheat bran were extracted and analyzed on a daily basis. T he activities of cellulase, xylanase and feruloyl esterase were also investigated during the fermentation process to find out their correlations. It was showed that free phenolic acids increased sharply after fermentation. The total phenolic content could reach 11561.30μg/g wheat bran, increasing by 169% than the unfermented wheat bran. Besides, positive correlations were found between the contents of phenolic compounds and the activities of xylanase and feruloyl esterase, revealing that synergistic effects of these two enzymes during fermentation can lead to higher contents of phenolic compounds.2. Analysis of phenolic compounds contents and the antioxidant activities in unfermented and fermented wheat branDifferent forms of phenolic components in wheat bran were analyzed by HPLC respectively. Furthermore, DPPH radical scavenging assay, reducing power assay and anti- lipid per oxidation assay were conducted to analyze the antioxidant activities of phenolic components. It was showed that Aspergillus awamori could release the bound form of ferulic acid from wheat bran after fermentation, and increased the content of free phenolic components sharply. Besides, it was indicated that phenolic components with high concentrations of caffeic acid, syringic acid as well as ferulic acid exhibited higher antioxidant activities.3. Antibacterial activities of phenolic compounds in unfermented and fermented wheat branOxford cup method was applied to study antibacterial activities of phenolic compounds in unfermented and fermented wheat bran. Inhibiting effects on Staphyloccocus aureus Rosenbach, E. Coli O157 and Bacillus subtilis were studied in this article. It was showed that alkaline-hydrolysable phenolic components have the most obvious inhibiting effects on the bacteria mentioned above, followed by acid-hydrolysable phenolic compounds and bound phenolic compounds hydrolyzed by acid. The comparison of inhibition effects of alkaline-hydrolysable phenolic components was: unfermented wheat bran > wheat bran fermented by Aspergillus awamori strain GIM3.4>wheat bran fermented by Aspergillus awamori strain GIM3.266>wheat bran fermented by Aspergillus awamori strain GIM3.5.This research revealed the correlations between contents of phenolic compounds of unfermented and fermented wheat bran and activities of three types of enzyme for the first time. Besides, contents of phnolic acids in different forms of phnolic compounds and their oxidation resistance and bacteriostasis were also studied. These findings can help to improve the value in use of wheat bran and provide theoretical basis for its further research and development.