Annually, agri-food industries generate significant amounts of waste, particularly from plant-based and dairy sources. Although these wastes can pose environmental and economic management challenges, they are also rich in bioactive components, making them cost-effective substrates for microbial growth and a natural source of high-value compounds. In this context, eleven by-products derived from fruit, vegetable, and dairy processing were selected, along with ten different strains of lactic acid bacteria (LAB), to assess their potential as alternative substrates for microbial growth and biomass production. All matrices were subjected to various physical pretreatments in order to evaluate their influence on LAB proliferation. Later, the strains were incubated at a controlled temperature, and the bacterial growth was monitored for 24 hours using spectrophotometry.

Matrix–strain combinations analysis have highlighted the most efficient pairings for supporting microbial growth. These preliminary findings provide valuable insights for the development of innovative, cost-effective, and eco-friendly growth media, promoting the adoption of circular economy practices, and contributing to waste reduction.