Lactic acid production from tomato pomace fermentable sugars using innovative biological treatments

The organic residues from agro-food sector can be transformed into valuable economic resources rather than representing an unmanageable waste, whose disposal in landfills contributes to increase both soil pollution and the greenhouse effect. With this in mind, the aim of the investigation is to design eco-friendly compatible innovative biological processes for producing lactic acid (LA) from fermentable sugars using as substrate tomato pomace. In the first part of the investigation, we show the physico-chemical characterization of tomato pomace produced in the 2017 season with or without thermal pre-treatment. pH, total and volatile solids content, sugars and cellulose are measured. The microorganism consortia suitable for lactic acid production are selected from buffalo dung, and compared with commercial strains of lactic acid producing bacteria. Both bacteria consortia are used as inoculum for the anaerobic fermentation of tomato pomace as sole substrate for producing fermentable sugars and convert them in LA. Sugars are measured by a spectrophotometric-coupled enzyme assay and LA by HPLC with electrical conductivity detector. The molecular analysis of the isolated bacteria is performed by using the denaturing gradient gel electrophoresis (DGGE). Anaerobic fermentation of tomato pomace is also performed using different initial pH values of the substrate. The final goal is to design biological processes aimed at achieving the highest LA recovery yields