Functional properties of Rhizopus oryzae strains isolated from agricultural soils as a potential probiotic for broiler feed fermentation.

The most crucial and expensive fragment in the broiler chicken production industry is the feed. Because of the rising demand, finding a cheap and effective feed is an urgent necessity. Fermentation of broiler feed by probiotic fungal starters can enhance the nutrient's availability and digestibility while preventing pathogenic growth. In this study different Rhizopus spp. have been isolated from agricultural soils around Izmir, Turkey, and tested for their probiotic potential and fermentative capacity. The isolated Rhizopus strains first underwent microscopical fluorescent investigation to exclude endofungal bacterial presence, then, those without endofungal bacteria (totally 82) were tested for antimicrobial activity counter bacterial and fungal pathogens. The ones with wide-spectrum antimicrobial activity (totally 10) were tested for gastrointestinal tolerance and antioxidant ability. Upon phenotypic and genotypic identification, the 10 isolates were found to belong to Rhizopus oryzae species. While all 10 strains showed variable gastrointestinal tolerance and antioxidant activities, three of them (92/1, 236/2, and 284) had relatively high antioxidant activity. Upon fermentative capacity assay, compared to unfermented commercial feed, there was a general decrease in crude fiber content by 56% after fermentation by 92/1 isolate for 4 days and 236/2 isolate for 2 days. The highest increase in crude protein content (by 14.5%) occurred after a 4-day fermentation period by 236/2 isolate. The highest increase in metabolizable energy was 8.64%, by the 284 isolate after 2 days of fermentation. In conclusion, the three strains showed good probiotic properties and fermentative capacities hence can be beneficial for the poultry industry.