Valorization of liquid waste generated from biogas production as supplemental material in shiitake mushroom cultivation

The aim of the study is to investigate the effect of supplementation of growing media with different levels of biogas liquid waste (BLW) on the production of two commercial strains of shiitake (LE-Agroma and LEHomegreen). The strains were cultivated on oak sawdust (OS) soaked with water containing 0, 2.5, 5, and 10% percentages of BLW and the effect of different treatments was evaluated for cultivation cycle, yield, biological efficiency, nutritional content, macro- micro element contents and accumulation of heavy metals in the fruiting body. The shortest cultivation cycle for shiitake mushrooms, i.e., 82.3 and 75.6 days, was obtained with 10% BLW treatment in LE-Agroma and LE-Homegreen, respectively. The strains displayed the highest yield and BE (297.82 g kg- 1-87.6% and 225.89 g kg- 1-75.8%, respectively) in the same treatments. The use of BLW positively affected the fat, carbohydrate, macro and micro element contents of shiitake strains, whereas its increased supplementation inversely affected the protein content of the fruiting body. Accordingly, the left-over BLW after biogas production can be successfully used as an additive to cultivate shiitake mushrooms, with no risk to human health.