Conversion of conifer wastes into edible and medicinal mushrooms Suki C. Croan Lentinus edodes, compared to 13 and 25 Abstract percent of wheat and milk, respectively Mushroom-producing white-rot fungi can be used to convert woodwaste into gour- (Ogundana and Okogbo 1981). Pleu- met and medicinal mushrooms. White-rot fungi do not always readily colonize on coni- rotus mushrooms are considered to be fer wood because of its extractives content. This study evaluated the resinous extractive one of the most efficient producers of content of loblolly pine ( Pinus taeda), ponderosa pine ( Pinus ponderosa ), and an un- food protein (Ogundana and Okogbo known species of southern yellow pine before and after treatment with the extrac- 1981, Manzi 1999, Dabbour and Tak- tive-degrading fungi Aureobasidium spp., Ceratocystis spp., and Ophiostoma spp. buri 2002) and an excellent source of Fungal treatment removed 70 to 99.9 percent of extractives. Scanning electron micros- dietary fiber (Cheung and Lee 2000, copy showed heavy mycelial growth ofthe colorless isolate Ophiostoma piliferum, with Mattila and Pizzoferrato 2000). Pleuro- good sporulation, on the surface of loblolly and southern yellow pine chips, in the resin tus mushrooms also produce vitamins canals, and in the parenchyma cells within 4 to 5 days. The treated wood chips were used (B1, B2, B12, C, D, folate, and niacin) to cultivate lignolytic mushroom-producing, white-rot basidiomycetes of various (Mattila et al. 2001) and mineral ele- Pleurotus species and two other fungi, Grifola frondosa and Hericium erinaceus. The ments (Manzi 1999, Mattila et al. 2001). results show that lignolytic white-rot basidiomycetes can easily colonize and produce These nutritious and medicinal mush- mushrooms on treated conifer wood chips. rooms (Cochran 1978, Chang and Bus- well 1996, Ishisuka et al. 1997, She et al. 1998, Wasser and Weis 1999) are in great demand by the gourmet mush- room industry (Chang 1999). woodwaste, including thinned Pleurotus or oyster mushrooms has been The medical uses of Pleurotus mush- material from stagnated and overstocked increasing at a rapid rate worldwide. rooms include their potential to act as small-diameter wood, poses a serious Pleurotus mushrooms represent 14 per- antitumor agents (Cochran 1978; threat to forest health by increasing fuel cent of the total world production of ed- Gunde-Cimerman 1999; Kawamura et load, which can result in forest fires that ible mushrooms, amounting to 368,000 al. 2000; Zhang et al. 1994, 2001) and severely damage the ecosystem. In the tons in 1997 (Chang 1999). The produc- antifungal and antiviral agents (Gunde- year 2000, there were 122,827 fires, tion of Pleurotus mushrooms is a rela- Cimerman 1999) as well as their ability 8,422,237 acres burned, andanestimated tively new enterprise in the United to lower cholesterol (Chovot 1997, $1.3 billion in fire control costs (Bos- States; 88 1 tons were produced in 1995, Cheung 1998, Bobek et al. 1998a, Was- worth 200 1). At the same time, the global an increase of 94 percent from the previ- ser and Weis 1999) and reduce colon ous year (Royse 1997). demand for energy and nutritious food carcinoma (Bobek et al. 1998b, Gunde- has been increasing, and there is a grow- Pleurotus mushrooms are very effi- Cimerman 1999). Pleurotusmushrooms are fast colonizers that degrade a wide ing shortage of natural resources. cient producers of protein. Protein con- variety of lignin in lignocellulosic Thinned material from stagnated and stitutes 30 percent of the dry weight of woodwaste. They produce extracellular overstocked small-diameter wood stands Pleurotus mushrooms and 18 percent of can serve as a valuable resource for the production of nutritious gourmet and The author is a Mycologist, USDA Forest Serv., Forest Prod. Lab., One Gifford Pinchot medicinal mushrooms. Drive, Madison, WI 53726-2398. The author wishes to thank the following staff at the Forest White-rot fungi that produce edible Prod. Lab. for their assistance: Roger C. Pettersen for analysis ofwood extractives, Thomas A. Kuster for scanning electron microscopic examinations, and John Haight for technical assis- and medicinal specialty mushrooms tance. This paper was received for publication in August 2002. Article No. 9532. have been cultivated from hardwood in ©Forest Products Society 2004. Asia for centuries. The production of Forest Prod. J. 54(2):68-76. 68 FEBRUARY 2004 enzymes, including lignin peroxidase, ids, resin acids, sterols, and steryl the Forest Products Laboratory. A color- manganese peroxidase, and laccase. esters), and waxes, alkaloids, and tropo- less isolate of Ophiostoma piliferum These enzymes are nonspecific with re- lones, which are found in parenchyma (Cartapip 97) was obtained from gard to substrate and are referred to as cells and in the lumen of other cells AgraSol, Inc. (Raleigh, North Carolina). lignin-modifying and/or lignin-degrad- (Sjostrom 1981, Zabel and Morrell ing enzymes. As a result of fungal ligno- 1992, Gao and Breuil 1995). The fungi were maintained on 1.5 per- lytic action on wood, the spent substrates Pleurotus mushrooms have been cul- cent (w/v) malt extract (Bacto, Difco, together with the remaining fungi can tivated on various agricultural lignocel- Detroit, Michigan) and 2 percent (w/v) become a source of hemicelluloses and lulosic wastes or hardwood but never on agar (Bacto, Difco; MEA). Malt extract cellulose that can be used as carbohy- conifer wood. The primary objective of agar 90-mm-diameter plates were inoc- drate for animal feed (Bisaria et al. our research was to evaluate the my- ulated with a mycelium/agar plug (6 mm 1997) or fertilizers (Stewart et al. 1998). celial growth of mushroom-producing diameter) of a young, actively growing Southern yellow pine (SYP) consists Pleurotus species on conifer woodwaste margin of the colony at the center of the of 11 species: longleafpine ( Pinuspalu- after treating the wood with extractive- plate and incubated at 24°C in the dark stris), short leaf pine ( P. echinata ), slash degrading fungi. The secondary objec- for 1 to 2 weeks or until mycelial growth pine ( P. elliottii ), southern Florida slash tive was to convert conifer wood resi- had covered the entire surface of the pine ( P. elliottii var.densa), loblolly pine dues, woodwastes, and underutilized plate. (P. taeda ), pitch pine ( P. rigida ), spruce forest resources into a value-added re- pine ( P. grabra ), Virginia pine ( P. source for the production of gourmet Treatment of chips virginiana), sand pine ( P. clausa ), pond and medicinal mushrooms. Loblolly pine (Pinus taeda) chips pine ( P. serotina ), and table mountain were obtained from Bowater, Inc. (Cata- pine ( P. pungens ). Four of these species Methods and materials bwa, SC). Chips of an unknown species (loblolly pine, short leaf pine, long leaf of SYP ( Pinus spp.) were obtained from pine, and slash pine) account for about Fungi the Bienville National Forest in Missis- 93 percent of all standing timber in the Dikaryotic isolates of the following sippi. Ponderosa pine ( P. ponderosa) southeastern and south-central states mushroom-producing white-rot fungi chips were obtained from the Coconino (Hoadley 1990). SYP usually contains a were obtained from the culture collec- National Forest near Flagstaff, Arizona. high concentration of wood extractives tion of the Center for Forest Mycology All chips were frozen until used. or pitch deposits, ranging from 3 to 9 Research at the Forest Products Labora- Small-scale treatment. – One hun- percent of total dry weight of the wood tory (USDA Forest Serv., Madison, Wis- dred grams (dry weight 45% to 50%) of (Koch 1972). In exceptional cases, the consin): Grifola frondosa (Dicks:Fr.) frozen SYP chips of various sizes (0.5 to extractives may constitute up to 40 per- S.F.Gray (FP-101988, SC 10), 2 cm by 0.2 to 0.25 cm) and distilled wa- cent, depending on the season when they Hericium erinaceus (Bulliard: Fries) ter were added to Pyrex storage dishes were harvested (Zabel and Morrell Persoon (FP- 140075, SC 13), (Corning No. 3250) to produce a final 1992). Some extractives (i.e., monoter- Pleurotus citrinopileatus (Singer) moisture content of 60 percent. Each penes) are toxic to certain fungi and in- (FP-102361, SC 17), P. cystidiosus O.K. dish was autoclaved and inoculated with sects (Raffa and Smalley 1995, Payne et Miller (FP-140088, SC 18 and FP- actively growing mycelia from half an al. 2001); other extractives impart color 140088, SC 19), P. euosmus (Berkley MEA plate inoculated with the extrac- and fragrance to wood. apud Hussey) Saccardo (FPRL-66,SC tive-degrading fungi Aureobasidium Wood-extractive-degrading fungi are 20), P. ostreatus (Jacquin: Fries) spp. or Ceratocystisspp. A colorless iso- initial wood colonizers that cause black Kummer (FP-101509, SC 21 and late of Ophiostoma piliferum (Cartapip 8 discoloration in sapwood as well as in FP-140084,SC 23), P.populinus Hilber 97) was inoculated 2 × 10 spores (1 ×) 8 wood chips, logs, sawn timber, veneer, and Miller, (FP-102755, SC 24), P. and 4 x 10 spores (2×) per storage dish. sawdust, and wood products. The fungi pulmonarius (Fries) Quelet (RLG- After thorough mixing, the inoculated penetrate rapidly and deeply into the 10645, SC 25 and FP-140087,SC 36), P. wood chips were incubated at 24°C in sapwood of conifers, assimilating avail- sapidusKalchbr., (FP-4-103, SC 27, FP- the dark for 30 days and then autoclaved able nutrients (primarily nonstructural 140080, SC 28, and FP-140094, SC 55), to kill the extractive-degrading fungi. wood components), but they have little and P. sajor- caju (Fr.) Sing. (FP- The experiment was performed in tripli- or no effect on the cellulose, hemicellu- 140078, SC 29). cate. lose, or lignin content ofthe wood (Sjos- Pleurotus cornucopiae (Paulet ex To evaluate the growth of mushroom- trom 198 1; Blanchette et al.