**7. Effects of some factors for the growth of ligninolytic fungi**

Although there are microorganisms capable of secreting this type of extracellular enzymes, the efficiency of complex degradation processes depends on the potential of the degrading organism, its oxidative mechanisms and culture conditions. The

### *The Roll of Different Kind of Fungi to Eliminate Lignin and Organochlorines: A Review DOI: http://dx.doi.org/10.5772/intechopen.105162*

problem that persists today is the slow cultivation of fungus species in wood and the sensitivity to growing conditions [17]. These extracellular oxidoreductase enzymes are generally secreted in low amounts. The degradation of fungal lignin is considered as a secondary metabolic event that is triggered when the indispensable nutrients like nitrogen are depleted [38].

Has been seek the way to increase the enzyme production by the different fungus strains and some reports that such increase can be achieved by modifying the source of carbon and nitrogen in the medium. Since the cost of enzymes is very high, this is a limitation in industrial use, however, the use of agricultural waste not only lowers cost, but also solves an environmental problem [34].

Therefore, the production of lignin-modifying peroxidase has traditionally been studied in media with low nitrogen concentration. Phenol rich but also nitrogen rich crops often increase laccase activity in white rot fungi and a complex nitrogen source such as peptone is generally required for efficient laccase production [38]. Copper is a known inducer of fungal lacquer activity. Its promoter effect on Lac production can be explained at the folding and post-translational level of proteins since the fungal laccases contain four copper atoms at two active redox sites. Transcriptional activation of the Lac genes by copper with several white rot fungi has also been demonstrated [38].

In general, and as happen with other enzymes, the enzymatic activities and biodegradation rates are influenced by pH, temperature, substrate concentration, presence of mediators, for example, 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and veratryl alcohol, cofactors such as Cu2+ and Mg2+, inhibitors such as organic acids, for example, citric, oxalic, and tartaric acid [28]. Molecular cloning studies of ligninolytic enzyme genes, such as the *Ganoderma lucidum* laccase gene, expressed in *Pichia pastoris*, have been carried out, taking into account the effects of temperature, pH, and nitrogen source on the expression of the enzyme in *P. pastoris*, obtaining that at a pH of 7.0 and a temperature of 20–30°C the Lac was stable [33].

It is now considered that extracellular lignin-modifying enzymes (Lac, LiP, MnP, and VP) together with new peroxidases containing a hemo group secreted by white rot fungi may be crucial for the biodegradation of lignocelluloses and lignocelluloses peroxidases secreted by hemo-containing fungi are oxidizing and biocatalyst proteins for the conversion of lignin-like compounds and aromatic compounds, and show specificity against a wide range of organic and inorganic compounds. Lignin modifying peroxidases (LiP, MnP, and VP) are structurally related to hemo-glycoproteins belonging to the family of fungal hemo-peroxidases [38].
