In this study, A. awamori was selected as the starter microorganism to biotransformed phenolic-rich LPE. After fermentation, the phenolic content of the water fraction dramatically decreased within the first 6 days and then increased on the15th days. Degradation and absorption of phenolics available used as a carbon source by A. awamori to maintain its growth may account for the decrease in the phenolic content within the first 6 days . Natural degradation of phenolics in LPE without A. awamori was observed (data not shown). This is consistent with the finding of Huang et al. , who reported decrease of total phenolic content in black soybean koji during storage. Previous reports [12, 20, 21] pointed out that some hydrolases (e.g. β-glucosidase, β-Xylosidase and α-arabinofuranosidase) present in A. awamori were able to crack the linkages between phenolics and their glycosides to produce more hydrophobic compounds, which might account for the increased hydrophobic phenolic compounds in the present study. Similarly, a change in the content of flavonoid content of the water fraction of LPE was observed (Figure 1). Hund et al.  and Stoilova et al.  reported that some flavanoid-degrading enzymes such as quercetin 2,3-dioxygenase was present in A. niger or its variant. These enzymes can cleave C2 and C3 positions in B ring of quercetin to form 2-protocatechuoylphloroglucinol carboxylic acid . The decrease in flavonoid content in the A. awamori-fermented LPE might be due to the action of these enzymes.
The effect of A. awamori on antioxidant properties of various plant material, such as black bean , wheat grain  and rice , were previously investigated. Among those studies, the increase in phenolic content after fermentation was supposed to be responsible for enhanced antioxidant activity. In this present study, DPPH scavenging activity of the LPE water fraction increased greatly while phenolic content decreased within the first 3 days. Moreover, a slight increase of phenolic content coupled with enhanced DPPH scavenging activity was observed in the LPE ethyl acetate fraction, which indicated that some compounds with higher DPPH scavenging capacity were produced after fermentation.
Plasmid DNA protection of LPE against Feton-reaction mediated breakage was used in this study. The water fraction of A. awamori-fermented LPE exhibited much higher DNA protection effect than the non-fermented fraction. However, no such effect was observed from both the A. awamori-fermented and non- A. awamori-fermented ethyl acetate fractions. Aqueous extract rather than organic solvent extract of plant tissues such as black gram husk , Asplenium ceterach, and areca inflorescence  were reported to possess DNA protection activity. In this study, the results concerning DNA protection activity was not completely consistent with DPPH radical scavenging activity. Zhang  demonstrated that no significant correlation between DNA protection activity and DPPH radical scavenging activity was observed. Thus, application of DNA protection capacity to antioxidant activity evaluation was needed to be elucidated further.
To further understand the effect of the fermentation on individual phenolic compound, the phenolic profiles of the A. awamori-fermented and non-A. awamori-fermented LPE were determined by HPLC. The HPLC chromatogram revealed that the main phenolics present in non-A. awamori-fermented LPE were procyanidin B1 (Peak 5), epicatechin (Peak 8) and epicatechin-3-gallate (Peak 10), which were also reported by Zhang et al.  and Zhao et al. . Great amount of compounds eluted as a hump at the retention time of 15−35 min was in agreement with the report of Roux et al. , who demonstrated the hump as proanthocyanidins with different polymerization degree. After the fermentation of A. awamori, many peaks disappeared in the water fraction but appeared in the ethyl acetate fraction, which might be attributed to β-glucosidase produced by A. awamori as the enzyme can hydrolyse glycosided flavonoids to more hydrophobic aglycones. This assumption was confirmed by the appearance of new compounds (Compounds 1’, 2’ and 4’) after 3 days, and the presence of quercetin (Peak 6’) and the absence of quercetin-3-glucoside (Peak 9) after 6 days of fermentation. In this study, A. awamori could cleavage the C4 and C8 bond of procyanidin B1 and then form catechin and epicatechin which reduced the content of compound 5 but increased the contents of compound 6 (catechin) and compound 7 (unknown compound) on the 3rd day of the fermentation (Figure 2b). Meanwhile, B-type procyanidin and catechin were reported to be further metabolized to more hydrophobic A-type procyanidin by some phenol oxidase [34, 35], which may account for the appearance of several compounds in the ethyl acetate fraction (Figure 2c).
A. awamori generally recognized as safe filamentous fungi  was widely present in traditional fermented foods (i.e. miso, natto and tempeh) in East Asia. In the present study, A. awamori was used to bioconvert the phenolics-rich LPE. To the best of our knowledge, the study was the first report on the increased antioxidant activity and DNA protection effect in relation to the conversion of phenolics of litchi pericarp by A. awamori. This work provided a better way of utilizing litchi pericarp as a readily accessible source of the natural antioxidants in food industry. The fermentation technology can further extend to the bioconversion of phenolic compounds in agriculture-derived by-products. Further investigation into the biochemical pathway of these phenolic compounds converted by A. awamori will be needed.