CO2 evolution rate during solid-state fermentation for preparation of tomato pomace as a poultry feed ingredient

α-Tocopherol in tomato pomace fed to broilers could retard lipid oxidation in processed, heated and/or stored meat. However, in order for tomato pomace to be a value-added feed ingredient for poultry, this agricultural byproduct must contain reduced cellulose, hemicellulose and lignin, possibly achieved by amendment with Mn (487 μM/g substrate) and treatment with Pleurotus ostreatus under solid-state fermentation. Research was conducted to assess the O2 consumption rate and the CO2 evolution rate in tomato pomace treated with Pleurotus ostreatus without and with Mn to determine if peak colonization rate (for heightened delignification) was delayed by amendment. Results revealed that (1) one mole of O2 was consumed for each mole of CO2 evolved, (2) the peak CO2 evolution rate for all treatments occurred between 300 to 350 h (12.5 to 14.6 d) and (3) the peak CO2 evolution rate and the cumulative evolution rate were not delayed by Mn addition. Thus, when Mn was amended to tomato pomace, the metabolic activity of P. ostreatus was reduced, thereby overriding potential improvements in pomace delignification and in-vitro digestibility. An atmosphere with >20% O2 and lower levels of Mn are needed to enhance delignification of tomato pomace for use in poultry feed.