*3.1.1. Decomposition of organic matter*

The occurrence of phenolic compounds in water is sometimes due to the decomposition of dead plants and animals in the water bodies; or as a result of runoff from the land where the decomposing materials are washed into water bodies. Phenolic compounds are components of many plant species, aquatic or terrestrial. Some of these compounds are formed from amino acids, present in hemicelluloses of some plants, under ultraviolet light irradiation. For instance, willow bark is known to contain a certain amount of salicylic acid [11]. Green and red marine algae also contain macromolecules of phenolic compounds. Hydroxybenzene, for example, is produced due to decomposition of organic matter [12]. The body of humans and animals, without any external exposure, produces phenol which finally gets excreted. Thus, the meta‐ bolic waste products of humans and animals also contain phenol [13]. Phenol is produced in the gut of mammals as a result of the transformation of tyrosine in their digestive tract [14]. The compounds are also components of many food stuff including fruits and vegetables. Phenol is found to be present naturally in coal tar and creosote. It is also produced during natural fires, and through benzene degradation in the atmosphere under the influence of ultraviolet light radiation [14]. Direct decomposition of these materials in water or indirect introduction from runoffs and rainfall result in the pollution of the water bodies with these compounds.

### *3.1.2. Synthesis by microorganisms*

The potential of microorganisms to degrade naturally occurring substrates into phenolic compounds, particularly hydroxybenzoate, is well established [15]. Debaryomyces hansenii is noted for its ability to convert ferulic acid into varied phenolic compounds in the presence of glucose and nitrogen. Debaryomyces hansenii metabolism of ferulic acid was identified by Max et al. [16] to produce 4‐vinyl guaiacol, vanillic acid, acetovanillone, ferulic acid, vanillin and 4‐ethylguaiacol, while Shashwati et al. [17] noted the ability of Streptomyces sannanen‐ sis to convert ferulic acid to vanillic acid. Fermentation of plant extracts by microorganisms is also known to result in the formation of different types of phenolic compounds. A study involving the use of Lentinus edodes for the fermentation of cranberry pomace identified the formation of ellagic acid [18], while fermentation of ethanolic acid (obtained from oat) by a fungus, Aspergillus oryzae, produced caffeic and ferulic acids [19].
