Enhancing the Nutritional and Functional Properties of Auricularia auricula through the Exploitation of Walnut Branch Waste

As the third most edible fungus in the world, Auricularia auricular needs a lot of sawdust for cultivation; thus, it is a win–win method to develop waste wood sawdust suitable for black agaric cultivation. This study evaluated the growth, agronomic characters and nutritional quality of A. auricula cultured on different ratios of miscellaneous sawdust and walnut waste wood sawdust, and comprehensively analyzed the feasibility of cultivating black agaric with walnut sawdust using principal component method (PCA). The results showed that the macro mineral elements and phenolic substances in walnut sawdust were significantly higher than those of miscellaneous sawdust by 18.32–89.00%. The overall activity of extracellular enzymes reached the highest when the ratio of the substrate was 0:4 (miscellaneous sawdust: walnut sawdust). The mycelia of 1:3 substrates grew well and fast. In addition, the growth cycle for A. auricula was significantly lower for 0:4 (116 d) than for 4:0 (126 d). Then, the single bag yield and biological efficiency (BE) were highest at 1:3. Moreover, the nutrients and mineral elements of A. auricula cultivated in walnut sawdust were significantly higher than that of miscellaneous sawdust, expect for total sugar and protein, and the highest overall value was found at 1:3. Finally, the results of comprehensive evaluation by PCA showed that the D value was the highest when the substrate was 1:3 and the lowest when the substrate was 4:0. Therefore, the substrate ratio of 1:3 was the most suitable for the growth of A. auricula. In this study, the high yield and quality of A. auricula were cultivated by waste walnut sawdust, which provided a new way to utilize walnut sawdust.