Recycling spent Pleurotus eryngii substrate supplemented with Tenebrio molitor feces for cultivation of Agrocybe chaxingu

Recycling spent Pleurotus eryngii substrate supplemented with Tenebrio molitor feces for cultivation of Agrocybe chaxingu Xian-lu Zeng 0 1 Fei Han 0 1 Jing-li Ye 0 1 Yan-mei Zhong 0 1 0 Shantou Institute of Quality and Metrology Supervision Testing , Shantou 515041 , China 1 School of Life Sciences, Jiaying University , 100 Meisong Road, Meizhou 514015 , China Purpose In the industrialized production of mushrooms usually only one flush of fruitbody is harvested, so that nutrients and energy in the substrate is not fully exploited. In this study, the spent Pleurotus eryngii substrate was recycled for the cultivation of Agrocybe chaxingu under ambient temperature. Method Six formulae were tested: (1) Control: 98% spent substrate, 1% sucrose, 1% lime; (2) Control ? 10% wheat bran; (3) Control ? 20% wheat bran; (4) Control ? 10% T. molitor feces; (5) Control ? 20% T. molitor feces; (6) Control ? 10% wheat bran ? 10% T. molitor feces. Results Two flushes of fruitbody were harvested, the control substrate resulted in a biological efficiency of 40.42%; the formulae with supplementation of 10% wheat bran, 20% wheat bran and 10% T. molitor feces significantly increased biological efficiency to 52.50, 54.61 and 51.56%, respectively, and supplementation of 20% T. molitor feces, or 10% wheat bran plus 10% feces further significantly increased biological efficiency to 62.95 and 61.10%, respectively. All supplemented substrates had significantly higher cellulose and laccase activity than the Control (cellulase 0.10 U/g; laccase 41.00 U/g), which were 10% wheat bran (0.15 U/g; 72.67 U/g), 10% T. molitor feces (0.17 U/g; 98.33 U/g), 20% wheat bran (0.22 U/g; 76.00 U/g), 20% T. molitor feces (0.27 U/g; 87.00 U/g), 10% wheat bran plus 10% T. molitor feces (0.25 U/g; 97.67 U/g), respectively. Conclusion Spent Pleurotus eryngii substrate was promising for cultivation of Agrocybe chaxingu, especially when supplemented with 20% T. molitor feces, or with 10% T. molitor feces plus 10% wheat bran. Spent mushroom substrate; Fruitbody; Biological efficiency; Cellulase; Laccase Introduction In the industrialized production of low temperature fruiting type mushrooms like Pleurotus eryngi and Flammulina velutipes, usually only one flush of fruitbodies is harvested (biological efficiency 60–65%) because the biological efficiency of the successive flushes are not high enough (approximately 30%) to make a profit where facilities and air cooling systems are expensive. Currently, most of the spent substrate is burnt to generate steam for substrate sterilization and heating of mushroom farms, some spent substrate is used as organic fertilizers in orchards. Nutrients and energy in the substrate is not fully exploited, as evidenced by over 100% total biological efficiency in non-industrialized mushroom production under natural environmental conditions where 3–4 flushes were harvested (Philippoussis et al. 2001; Mandeel et al. 2005) . In recent years, many experiments have been conducted to recycle the spent substrate for cultivation of other mushrooms (usually high temperature fruiting types) (Royse 1992; Li 2013) . Agrocybe chaxingu (in some previous cases mistakenly termed A. cylindracea or A. aegerita) (Callac et al. 2011) is a popular mushroom with a sweet aroma and many medicinal benefits. It is an antioxidant (Choi et al. 2009) , possessing properties that aid the curing of cancers (Hyun et al. 1996) , diabetes (Lee et al. 2010) , etc. With a view to recycle spent P. eryngii substrate for cultivation of other mushrooms in a low cost way, in the present study, A. chaxingu was chosen because it is a moderate temperature fruiting type mushroom suitable for cultivation at a broad range of ambient temperatures for a period from late spring to autumn in south China. To formulate recycled substrate for A. chaxingu cultivation, the nutrient composition of spent P. erygnii substrate was analyzed and compared with the unused substrate. Tenebrio molitor rearing has expanded rapidly in China, mainly as animal and pet feed, and to a lesser degree for human consumption. The sand-like feces of T. molitor larvae contain digested fiber, crude protein (14–18%), crude lipid (15–18%) and minerals (Wang et al. 2012; Lee and Rho 2014) , therefore, T. molitor feces could be an ideal ingredient used for mushroom cultivation, but very few such studies were reported (Gan et al. 2008). Currently T. molitor feces is used mainly as garden fertilizer or livestock feed. The purpose of the present study was to test if the spent substrate of P. eryngii in the industrialized production setting was a good substrate for production of A. chaxingu; and the effect of supplementing 10–20% T. molitor feces or/and wheat bran in improving fruiting body yield. Material and methods A. chaxingu and spent P. eryngii substrate The experimental A. chaxingu strain was purchased from Xue Shan Er Precious Edible Mushroom Institute, Gutian county, Fujian province. Sp (...truncated)