Otimização do cultivo de bacillus SPP. para a produção sustentável de bioinsumos destinados a agropecuária.

Abstract

Given the growing demand for agricultural inputs with lower environmental impact, this study investigated the development and optimization of processes for producing microbial bioproducts for agriculture and livestock, integrating circular bioeconomy principles and leveraging agro-industrial waste. The research focused on the application of Bacillus subtilis, Bacillus licheniformis and Bacillus paralicheniformis species with proven biotechnological potential. The methodology was structured in two main stages.In the first stage, a central composite design (CCD) was used, with five formulations varying the concentrations of glycerol (2.5 to 7.5 g L⁻¹) and yeast extract (2 to 4 g L⁻¹), to optimize the submerged cultivation of B. subtilis, using glycerol as an alternative carbon source and yeast extract as a nitrogen source. The monitored variables included optical density at 600 nm (OD600), viable cell count (CFU mL⁻¹), pH and attenuated total reflectance infrared spectroscopy (ATR-FTIR). The data indicated that the interaction between glycerol and yeast extract was the main determinant of growth, with the formulation containing 7.5 g L⁻¹ glycerol and 4 g L⁻¹ yeast extract being the most efficient. Multivariate modeling using principal component analysis (PCA) and orthogonal partial least squares (OPLS) demonstrated the applicability of spectroscopy as a nondestructive, efficient tool for monitoring the culture. In the second stage, the three Bacillus species were assessed for growth under different temperature and nutritional conditions, followed by scale-up in 8 L bioreactors and tests of antimicrobial activity against zootechnically relevant pathogens. Final cell counts under optimal conditions were 1.76 × 10⁹ CFU mL⁻¹ for B. subtilis, 2.48 × 10⁸ CFU mL⁻¹ for B. licheniformis and 5.72 × 10⁷ CFU mL⁻¹ for B. paralicheniformis. B. subtilis and B. licheniformis displayed significant inhibitory activity against Staphylococcus aureus, Escherichia coli and Enterococcus faecalis, with average inhibition zones of approximately 11.3 mm and 14.7 mm, while B. paralicheniformis showed no relevant effect under the evaluated conditions.The scale-up process confirmed the reproducibility and technical viability of the system at larger scale. This work contributes to the development of environmentally sustainable technologies by demonstrating the feasibility of using agro-industrial waste to produce microbial bioproducts, combined with statistical optimization strategies and advanced analytical tools. We conclude that using residual glycerol as a substrate, coupled with promising microorganisms and spectroscopic monitoring, constitutes an effective strategy for generating sustainable bioproducts, strengthening more resilient, circular agricultural practices with reduced dependence on synthetic inputs in the Brazilian context.