Bio-transformed sawdust by white rot fungi used as a carrier for plant growth-promoting bacteria

This study assessed the bio-transformation of sawdust wood waste by a white rot fungi consortium and explores the use of the final product as a carrier for plant growth-promoting bacteria. During 75 days, Tabebuia roseae and Eucalyptus pellita (1:1) sawdust wood were used as growing substrates for Ganoderma lucidum, Pleurotus ostreatus, Trametes versicolor and Phanerochaete chrysosporium. Then, bio-transformed sawdust was evaluated as carrier of two strains of Enterobacter sp. and one strain of Stenotrophomonas maltophilia. Biologic activity and viability were determined at two storage temperatures (23–4 °C) for 60 days. Sawdust mixture was bio-transformed by white rot fungi. After 45 days, the carbon/nitrogen ratio was reduced up to 46 %, and 4.8 mg/g of CO₂ of residue was produced. Enzymatic activities attained a peak of 36.7 and 0.8 U g⁻¹ for laccase and manganese peroxidase, respectively in 45 days. Population of plant growth-promoting bacteria immobilized in bio-transformed sawdust wood decreased to 10⁵ CFU g⁻¹. However, this concentration and its biologic activity remained stable at 23 °C.