Fermentação em estado sólido da borra de café para o cultivo de shimeji-preto (Pleurotus ostreatus Jacq.)

Abstract

Solid-state fermentation is the type of natural fermentation where microorganisms develop with a small amount of cellulosic water in substrate, providing several products from sugarcane bagasse and coffee grounds, providing several products of high value in a food and medicinal, transform into a promising technical substrate for the cultivation of edible mushrooms in the use of vegetable and/or urban waste. Thus, we aimed at the production parameters of mushroom cultivation of coffee grounds and sugarcane bagasse in the percentages of 0%, 25%, 50%, 75% and 100% of coffee grounds (%, v/v) with 5 replications, totaling 25 experimental units (bags). The treatments were supplemented with 5% wheat bran and 10% sawdust on a dry basis (%, m/m), mixed with distilled water until reaching 68% moisture, bagged in a polypropylene bag 20 cm × 30 cm × 0.08 mm and sterilized in an autoclave at 121ºC at 101.32 kPa for an hour, then inoculated at a rate of 5% P. ostreatus spawn (strain PO/A02) of moisture substrate mass. The bags with the inoculated substrates were incubated in total darkness at 22.64 ± 2.02 ºC and 88.22 ± 5.99 % RH for 26 days. Then, they were induced with cuts. The experiment ended when 3 productive flows (harvests) were completed. The variables were mycelial growth (mm day-1 ), biological efficiency (%), production rate (% day-1 ), productive period (days), earliness (days) and organic matter loss (%). In addition, spent mushroom substrates (SMS) were analyzed in terms of pH, electrical conductivity (dS m-1 ), density (g cm-3 ), total organic carbon (mg g-1 ), dry matter (%) and ash (%). Results were provided by ANOVA and Tukey's test at 5% significance (P<0.05). We observed that the higher the proportions of coffee grounds, the lower mycelial growth and that adding a coffee ground to the treatments, there was an increase of almost 40% in biological efficiency, with respect to the coffee treatment or 100% sugarcane bagasse). The productive period was affected by the addition of coffee grounds, however, together with the biological efficiency, it provided a balance in the production rate, showing no difference between treatments, as well as for earliness and loss of organic matter. The coffee grounds SMS presented itself as an acidic substrate (pH≥4), of low density (<1 g cm-1 ) and low electrical conductivity (<1 dS m-1 ) which gives it a relative agronomic aptitude. We conclude that the solid-state fermentation of coffee grounds allows the cultivation of mushrooms, increases the biological efficiency, and generates a spent mushroom substrate with agricultural potential use, making it useful for its recycling.