Selection of microbial isolates for oxyfluorfen degradation in soil

Abstract

Brazilian agriculture is a key sector for economic development and food security; however, the intensive use of herbicides, particularly oxyfluorfen, has raised environmental concerns due to its persistence in soil. Microbial biodegradation represents a sustainable and promising alternative for mitigating such impacts. This study aimed to: select microbial isolates from soils with a history of oxyfluorfen application capable of surviving in media containing the herbicide; evaluate their oxyfluorfen degradation potential in vitro; identify biochemical markers associated with degradation efficiency; assess the degradation performance of selected isolates in soil via bioaugmentation; and identify the most efficient isolates at the species level. From 35 isolates, 20 demonstrated growth in the presence of oxyfluorfen. Among these, 65% were Gram-positive Bacillus spp., with 50% forming endospores; the remainder included Gram-positive cocci and yeasts. Multiple correspondence analysis of biochemical profiles did not clearly distinguish isolates by degradation capacity. However, isolates 14 and 4 showed superior performance, degrading 40% of the herbicide in 2.8 and 7.4 days (100 mg kg⁻¹), and 9.8 and 13.6 days (200 mg kg⁻¹), respectively. The most effective strains were identified as Bacillus licheniformis, Bacillus pumilus, Bacillus paralicheniformis, Micrococcus luteus, and Moesziomyces aphidis, the latter reported here for the first time.