ECOLOGICAL STUDIES ON TILE SYMBIOSIS OF TER ITOMYCES ...

7-3-1 INTRODUCTION
7.3 LIGNIN DDGRADATION
The bulk of energy in plant tissues in'tontained vithin a variety
of polysacchirideng sugars and lignin (SwLtt, ot n1o 1979)o PI&Ut tiesuO
contains
herbaceous Material
'up to 35% lignin, wood generally having higher levels than
part of the food materials of ternitese
(Table 7-3-1)-- Lignin therefore comprises a large
Licnin in a very complex polymer, the chemistry of which in
incoopletely understood (swift et al. 1979). TAgnins from different
sources may differ in their properties as units are linked by different
bondse They are a group of substances based on three-dimensional
complex aromatic polymers. The basic unit is a phanyl propane skeleton
with a hydrocarbon chain attached to a phenolic group, The chemistry
of ligning i*eo the variety of different bonds, the steric interference
provided by aromatic monomers with a variety of side chains, Its highly
branched and folded structure and Its hydrophobic riature, hinders
enzy=tic attacks resulting in lignin being the most slowly decomposed
of plant cell wall components (Swift ot al. 1979).
During secondary thickening lignin In laid down in the cell wall
thereby strengthening it. There is controversy as to whether some
degree of covalent bonding occurs between lignin and r-oolysaccharides
(Swift et al. 1979), The association of lignin and cellulose, which
may be largely physical, forms a mutually interpenetrating systom of
polymers, with the lignin formino a Icage9 around the carbohydrates,,
This aasociation protects CeIIUIOSO from attack by collulolytic enzymes
(La Face and Nutting 1973), and it in thought responsible for the
resistance of wood to microbial decay, except by fungi that have enzyme
systms capable of depolymerising lignin an vall an the carbohydrates
of *ood (Cowling 1961).
322.