Improvement of the valuable compounds of fish waste through solid-state fermentation with probiotics

• L. planetarium and P. acidilactici showed high viability on fish waste under SSF. • Adding malt beverage waste to fish waste increased co-culture viability by 33 %. • SSF enhanced the digestibility of proteins and antioxidant activity of substrate. • Fermented substrate has a good potential to use as a probiotic supplement. The nutritional value of fish waste is increased by using solid-state fermentation with probiotic strains. The highest number of viable cells were observed in the fish waste substrate by two strains, namely Lactobacillus plantarium (MT-ZH193) and Pediococcus acidilactici (CNCM I-4622 - MA 18/5 M). The temperature of 38 °C, the moisture of 42 %, and dried non-alcoholic malt beverage waste (MBW) at 5 % were the optimal values for desired variables to achieve maximum number of viable cells during the 48-hour fermentation (12.8 Log cfu/gdw). As the fermentation time increased, fat decreased by 28 %. The production of non-protein nitrogen increased as the true protein reduced during solid-state fermentation due to protease enzyme activity. The inhibition percentage of free radicals increased during the 48-hour fermentation as compared with the non-fermented sample. The first day of fermentation showed the highest level of protease enzyme activity. The results showed that fermented fish waste was a good choice as a feed additive for livestock and poultry due to its high concentration of protein and digestibility. It is also rich in non-protein nitrogen and peptides with antioxidant characteristics.