The development of a combined enzymatic and microbial fermentation as a viable technology for the spent coffee ground full utilization

This study demonstrated the innovative biotransformation aspect of spent coffee grounds (SCG) by application of the specific enzymatic cocktail with addition of lactic acid bacteria strain Lactobacillus rhamnosus (ATCC® 7469™). This bioprocess induced the improvement of the most of the quality parameters in SCG, causing a considerable increase in the bioactive contents (total polyphenols, chlorogenic acid, reducing sugars, free amino acids) and antioxidant activity, in comparison to the non-fermented SCG. Under the optimal conditions, at 37 °C, for 24 h, with 5% v/w of the inoculum employed, the polyphenols were increased for 67% (227.3 ± 3.3 mg GAE/g dm extract), reducing sugars 57% (277.9 ± 7.6 mg glucose/g dm extract), and α-amino nitrogen 80% (161.2 ± 9.8 mg/100 g dm extract), and the chlorogenic acid content was doubled, while the caffeine was reduced for 38%. Furthermore, the resulting product evinced a strong antioxidant activity detected via inhibition of DPPH radicals and reducing capacity assay (FRAP). The proposed technology is viable for a large-scale commercialization for utilization of easily accessible industrial residues, deriving a product with a nutritive formulation very desirable to be incorporated as an additive in food and feed industry.