Decomposition of14C-Labeled Maple and Spruce Lignin by Marine Fungi

Abstract

Fungi occur on driftwood, intertidal wood, manila rope, and other lignocellulosic substrates in marine and estuarine environments (Johnson and Sparrow, 1961; Hughes, 1975; Kohlmeyer and Kohlmeyer, 1979). Several Ascomycetes and Deuteromycetes cause soft rots of wood submerged in seawater (Barghoorn and Linder, 1944; Henningsson, 1976). The marine basidiomycete Nia vibrissa Moore & Meyers causes a white rot (Leightley and Eaton, 1979). Relatively few fungi can decompose lignin, an extremely complex aromatic polymer (Crawford and Crawford, 1980; Crawford, 1981). Fukuzumi et al. (1975) demonstrated that the marine hyphomycete Dendryphiella salina (Sutherland) Pugh & Nicot could degrade sodium lignosulfonate, an industrially modified lignin. Henningsson (1976), using sulfuric acid hydrolysis to measure lignin content, found a strain of Zalerion maritimum (Linder) Anastasiou that degraded 12% of the lignin in birch wood in six months. Methods involving the use of 14C-labeled lignocellulosic substrates have made it possible to determine the amounts of lignin degraded by microorganisms to CO2 and water-soluble products (Crawford and Crawford, 1976). Using [lignin'4C]-lignocelluloses prepared from Norway maple and blue spruce as substrates, we measured the degradation of hardwood and softwood lignin by pure cultures of 12 marine and estuarine fungi. The fungi tested were Asteromyces cruciatus Moreau & Moreau ex Hennebert (F-156), Ceriosporopsis halima Linder (R-592), Corollospora maritima Werdermann (R-19), Dendryphiella salina (DS-1), Diplodia oraemaris Linder (F-162), Halosphaeria mediosetigera Cribb & Cribb (R-575), Heleococcum japonense Tubaki (R-692), Humicola alopallonella Meyers & Moore (F-164), Monodictys pelagica (Johnson) Jones (F-80), Nia vibrissa (RDB-8), Papulaspora halima Anastasiou (F-167), and Zalerion maritimum (R-6). Twigs of Norway maple (Acer platanoides L.) and blue spruce (Picea pungens Engelm.) were incubated with a solution of L-[U-14C]-phenylalanine to label the lignin (Crawford and Crawford, 1976). [Lignin-l4C]-lignocelluloses were prepared from the twigs by grinding and extracting the phloem layer (Crawford and Crawford, 1976). Specific activities of the maple and spruce lignocelluloses were 539 and 902 dpm mg-l, respectively. Triplicate culture tubes containing 50 mg of labeled lignocellulose each were autoclaved and 15 ml of a sterile liquid medium [oven-dried Rila Marine Salts (Rila Products, Teaneck, New Jersey) 20 g, yeast