Effect of l-lactic acid from whey wastes on enzyme activities and bacterial diversity of soil

Abstract

The l-lactic acid obtained from a whey waste valorization process decreased pH and increased phosphate solubilization of a Plagic Antrosol soil. This behavior was reversible due to the complete and rapid degradation of lactic acid by soil microorganisms, leading to a strong soil biological stimulation. Both dehydrogenase (DHA) and acid phosphomonoesterase (APA) activities were also significantly stimulated, due to the stimulation of microbial activity, whereas the β-glucosidase activity was unaffected. There was also a shift in bacterial biodiversity with growth of bacterial strains using lactic acid as a C source. The bacteria enriched belonged to the plant growth-promoting bacteria (PGPb), such as Rhizobium and Azotobacter genus, involved in N2 fixation, and Pseudomonas and Bacillus genera, involved in phosphorous bioavailability. We conclude that lactic acid application improves fertility parameters on soils. Further research at field scale is needed to confirm these results.