Evaluation of antioxidants, total phenolics and antimicrobial activities of ethyl acetate extracts from fungi grown on rice straw

Abstract

Rice straw (RS) collected from Egyptian agricultural environment (Al-Masied village-Alsharqia Governorate-Egypt) was used as substrate for three fungal isolates namely: 4b, 1Asp, Pleurotus ostreatus NRRL 3501 and mixed culture of (4b, 1Asp). Isolates number 4b and 1Asp were identified using the molecular technique (18S rRNA). Isolate 4b and 1Asp, were identified as Trichoderma saturnisporum MN1-EGY and Aspergillus niger MN2-EGY, respectively. Trichoderma saturnisporum MN1-EGY extract exhibited the highest antimicrobial activity compared to the other fungal extracts. Total phenolic, antimicrobial and antioxidant activities were also determined from the ethyl acetate extract of rice straw inoculated by these fungi. The antioxidant scavenging concentration(SC50) values of the tested samples were 88.84, 91.45, 94.65 and 100.0µg/ml, respectively for Pleurotus sp., Aspergiluus niger, Aspergiluus niger + Trichoderma sp., and Trichoderma sp., after 15 days incubation, compared to ascorbic acid as positive control with SC50 value equal to 8.0 µg/ml. Total phenolic contents (TPCs) were maximum in Pleurotus sp. extract and found to be the most polyphenolic enriched sample (380.64 mg GAE/g dry extract) compared to extracts of Aspergiluusniger, Aspergiluus niger + Trichoderma sp., and Trichoderma sp. (261.89, 198.52, and 119.80 mg GAE/g dry extract), respectively. The GC-MS analysis has been also performed for the promising extracts.