Effects of substrate moisture content, log weight and filter porosity on shiitake (Lentinula edodes) yield Qing Shen a , Ping Liu a , Xin Wang a , Daniel J. Royse b, * a Kennett Square Specialties, 546 Creek Road, Kennett Square, PA 19348, United States b Department of Plant Pathology, 316 Buckhout Laboratory, Pennsylvania State University, University Park, PA 16802, United States article info Article history: Received 22 January 2008 Received in revised form 10 March 2008 Accepted 10 March 2008 Available online 15 May 2008 Keywords: Shiitake Mushrooms Sawdust logs Lentinula edodes Mushroom substrate abstract Production costs for shiitake (Lentinula edodes) are on the rise in the United States due to increasing expenses including materials, labor and energy. Increased yield and improved bioconversion of raw materials may improve grower profit margins and may help reduce the cost of shiitake to the consumer. Two crops (Crop 1 and 2) of shiitake were grown to evaluate effects of three substrate moisture contents (50%, 55% and 60%), two log weights (2.7 and 3.2 kg) and three porosities of bag filter (low, medium and high) on mushroom yield (g/log) and biological efficiency (BE). Yield data were collected under controlled environmental conditions for two breaks. The formulation with 55% substrate moisture gave the highest yield and BE. Higher mushroom yields were produced from heavier logs (3.2 kg), but BE was not signif- icantly affected. Filter porosity significantly affected yield and BE in Crop 1 but not in Crop 2. Significant interactions were observed for log moisture content  filter porosity for both crops. There were no sig- nificant two-way interactions observed for filter porosity  log weight or three-way interactions observed for moisture content  filter porosity  log weight. Maximum yields were obtained from 3.2 kg logs with a substrate moisture content of ca. 55% using medium or low porosity-filtered bags. This study may provide growers with additional information to better optimize production practices and become more efficient and competitive. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Production of shiitake (Lentinula edodes) worldwide increased more than 110-fold from 1936 (12,000 ton) to 1997 (1,321, 600 ton; Chang, 1999, 2005). Most of this increase occurred in the 1990 s. Shiitake accounted for 26% of production of various mushroom varieties worldwide and ranked second after the button mushroom (Agaricus bisporus) in 1997 (Chang, 1999). China is the major shiitake producer, accounting for 85.1% of total world pro- duction in 1997 (1,125,000 ton). In the United States, production of shiitake increased nearly 6-fold from 1987/1988 (540 ton) to 2006/2007 (3122 ton) (USDA, 2007). Most commercial production of shiitake is done on synthetic logs that contain hardwood sawdust, straw or corncobs as the ba- sal ingredients and starch-based supplements (10–60% dry weight) such as wheat bran, rice bran, millet, rye, and maize. Sufficient water is added to adjust the moisture content of the mix to about 60% (Royse et al., 1990; Royse and Sanchez, 2007). For commercial production, the mix is weighed and filled into plastic bags auto- matically by machine so that a uniform amount (usually about 2.7 kg) is added to each bag. The bags are made of heat-resistant polypropylene and contain a special filter patch of laminated microporous plastic. The microporus patch provides a microbial barrier to contaminants and allows gas exchange with the outside environment during substrate colonization (Royse and Sanchez- Vazquez, 2001). Growers, using two different methods, accomplish the substrate colonization phase either by completing initial spawn run and browning of the substrate inside the bag or by completing initial spawn run inside the bag and browning outside the bag. Browning is a term used by growers to describe the light-induced pigment that is formed by the leather-like mycelium (pellicle) on the surface of the log and is positively correlated with mushroom production (Matsumoto and Kitamoto, 1987). Browning in the bag generally re- quires a longer period of colonization, often 60–90 days before fruit- ing induction, while the second method requires only 42–49 days. Browning in the bag has the advantage of less handling and reduced management input while browning outside the bag requires special management techniques such as the control of carbon dioxide levels and humidity, as well as watering log surfaces to hasten browning. Browning outside the bag also allows for the use of higher levels of supplement and thus, potentially higher yields (Royse, 1997, 2001). In the United States, commercially available sawdust logs grown with shiitake mycelium range from 2.5 to 2.7 kg (wet wt) and vary somewhat in shape. The shape of the plastic bag filled with 0960-8524/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2008.03.067 * Corresponding author. Tel.: +1 814 865 7322; fax: +1 814 863 7217. E-mail addresses: qxs@comcast.net (Q. Shen), djr4@psu.edu (D.J. Royse). Bioresource Technology 99 (2008) 8212–8216 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech