Production of antioxidant by fungi using soybean milk residue (okara)

ISSN: 2319-7706 Volume 4 Number 2 (2015) pp. 847-866 http://www.ijcmas.com Okara is the residue obtained from ground soybean after removing the waterextractable fraction used to produce tofu or soymilk. The aim of this study was to evaluate the potential use of okara and to improve the health beneficial properties of soybean waste manufacture product (Okara). In this study, Three fungal isolates were isolated from okara to proved their virulence of pathogenicity, only one fungal isolate was found to be non-toxic and safe to use, this fungal isolate was identified as Trichoderma harzianum using traditional mycological method of identification and nuclotide sequence analysis of the inter transcribed spacer region. The screening for the production of antioxidant was carried out on Trichoderma harzianum in addition to the previously provided isolate of Aspergillus oryzea. The antioxidants were produced by solid-state fermentation using different solvents (water, ethanol, methanol, acetoneand di-ethyl ether) for extraction of antioxidant in a period of 10 days. In comparison with nonfermented okara, the protein and ash contents increased in all fermented okara samples than non-fermented one; the level of protein increased from 6.2 to 11.1% and from 6.0 to 10.1% using Aspergillus oryzea and Trichoderma harzianum, respectively. Also, the ash contents increased from 1.03 to 2.6% and from 0.72 to 1.6% using the previously identified Aspergillus oryzea and Trichoderma harzianum. While, the fat content reduced from 3.0 to1.4% and from 3.1 to 1.3 %, using Aspergillus oryzea and Trichoderma harzianum, crude fiber content reduced from 3.4to 1.5% and from 3.3 to 1.43 % using Aspergillus oryzea and Trichoderma harzianum. The water extraction of the antioxidant revealed asignificant increase in the total phenolic compounds ranged from 9.2 to 43.8 mg gallic/gm of okara after 5 days of fermentation using Aspergillus oryzea, while the total phenolic compounds increased from 6.5 to 27.2 mg gallic/gm of okara using Trichoderma harzianum. The extraction with diethyl ether revealed the lowest content of total phenolic compound which ranged from 1.5 to 8.7 mg gallic/gm of okara using Aspergillus oryzea after five days of fermentation. By using DPPH assay and their reducing power the antioxidant activity revealed an increase in all fermented okara samples in comparison with nonfermented one. The HPLC analysis of the water and ethanol extracts of the fermented okara using Aspergillus oryzea revealed a higher content of phenolic compounds in water extract; the cholorogenic (60117.6 mg/100g), caffeine (67876.86 mg/100g) and coumarin (45940.7 mg/100g).Also, the fermented okara with Aspergillus oryzea had a higher content of isoflavons in water extract; forment in (863.9 mg/100g), then genistein (434.7 mg/100g) and diadzein (476.1 mg/100g), but in ethanol extract the biochanin was the highest (831 mg/100g), followed by genistein (537.9 mg/100g) and diadzein (517.7 mg/100g). The antimicrobial activity of the fermented okara extracts using Aspergillus oryzea and Trichoderma harzianum, revealed a remarkable inhibition against all the tested and pathogenic bacterial and fungal species, using disc diffusion method K ey wo rd s Soya milk waste, Okara, Fermentation, Toxicity, Aspergillus oryzae, Antimicrobial activity, Phenolic compound, Antioxidant activity, Solvent, DPPH assay,