Sustainable bioconversion of rice straw into indole‑3‑acetic acid by Streptomyces coelicoflavus using response surface methodology

Abstract

Rice straw is an abundant agricultural waste that poses environmental disposal challenges and can be utilized for biotechnological applications. This study investigates the potential of actinobacteria to enhance rice straw biodegradation and sustainable indole-3-acetic acid (IAA) production, addressing the need for sustainable agricultural practices. Certain actinobacteria strains can effectively degrade rice straw while optimizing IAA production under controlled fermentation conditions. Twenty actinobacteria isolates were screened for lignocellulolytic enzyme activity, and ten were selected for rice straw biodegradation. IAA production was further optimized using response surface methodology based on temperature, pH, and agitation speed (RPM). Isolate S16 achieved a degradation rate of 68.75%, while S18 produced the highest IAA concentration (1040.625 μg/mL) under optimized conditions (25 °C, pH 9, 160 RPM). The purified IAA significantly improved Medicago sativa L. growth. Furthermore, the 16S rRNA gene sequence of isolate S18 was identified it as Streptomyces coelicoflavus strain NSH24 with accession number PP 320383.1. These findings underscore the potential of actinobacteria to efficiently convert agricultural waste into valuable bioproducts and promote sustainable farming practices. By transforming rice straw into high-value products like IAA, this approach contributes to a circular economy, offering an environmentally friendly solution for biomass utilization and agricultural sustainability.