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Composting
is a biological phenomenon causing the decomposition of organic substrates resulting
in stabilization at elevated temperatures due to biological heat production generating
a stable and final product that is free of pathogens. The natural
composting process is rather time-consuming, shortage of land and generation of
large quantity of waste require a quicker and effective treatment of these
wastes. Investigations have reported that inoculation of waste with cellulolytic
bacteria could be a considered a useful strategy for reduction in composting
timeperiod, enhance the properties of final product and achieve compost
stability (Lia et al., 2017). While, an improper inoculum may produce negative seed
influence and produce toxins for in-situ microorganisms 11–13. A suitable microbial inoculation can
improve the quality of the compost by generation of desired enzymes with decrease
in the operation time thus, reducing the production costs 4–9. As,
the major constituents of MSW is organic being cellulose, hemicellulose,
lignin, starch and protein compounds they undergo degradation by specific
enzymes. Microbial activity is achieved through the action of these
enzymes, responsible for
the hydrolysis of complex macromolecules present in the organic wastes. The process is then continued by
release of simple water-soluble compounds to support microbial
growth. A key role is
played by enzymes to mediate the biochemical process in the biological
degradation of organic matter1-2, determine
the physical and chemical changes in the compost affecting the rate of
composting and product quality of important nutritional elements like C,
N or P. This enzymatic activity can be directly influenced by factors such as pH, moisture,
nutrient availability, temperature and the chemical properties 17,22–24. The dehydrogenase activity is considered to be a general index
of biological activity on account of its role on the oxidative phosphorylation
process, and therefore in the respiratory metabolism of microorganisms (Delgado et al., 2004).
On the contrary, b-glucosidases, phosphatases, proteases and ureases are
related to specific cycles. b-Glucosidases are involved in the carbon cycle
through the hydrolysis of glucosides, while phosphatases release phosphate
groups from organic compounds. Proteases and ureases take part in nitrogen
mineralization. Both of them hydrolyze nitrogen compounds into
ammonia, using low molecular weight proteins and urea as a substrate,
respective. Therefore,
the enzyme activity characterization and quantification during composting is
essential to reflect the dynamics of the process in terms of organic matter decomposition
generating information about compost maturity3-4. In addition, the
enzymatic activity determination when compared to other analytical compost
stability evaluation techniques is easier, fast and less expensive5.
Also, the Mesophilic and thermophilic microorganisms affect the composting with
their succession being an important parameter for effective management of the
process6-7. At each phase of
composting, the enzymatic activities correlated with variations in composition
of microbial community (Ryckeboer et al., 2003a),
directly relate to rate of waste decomposition and,
therefore, provide information about
the product stability (Mondini et al., 2004) and maturity
(Tiquia, 2002, 2005).

 

Microbial

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activity is achieved through the action of the enzymes
that are responsible for

the hydrolysis of the organic matter. The enzymes
released by the microorganisms

during composting break down several organic matter
characterized by a

complex structure, finally leading to the solubilisation
of simple water soluble

compounds 3. As a consequence, enzymatic activities
give information on the

rate of decomposition of organic matter and, therefore,
on product stability 1

4. Important enzymes involved in the composting process
include dehydrogenase

which reflects microbial activity, B-glucosidases which
hydrolyze glucosides,

urease involved in N-mineralization, and phosphatases
that remove

phosphate and sulfate groups from organic matter 3 4.
Characterizing microbial

communities along the process is important for achieving
the effective

management of a composting process and it may provide
valuable information

regarding process evolution and biodegradation rate 5
6. The investigation of

the significant enzymes (e.g., dehydrogenases, ?-glucosidases,
phosphodiesterase

and ureases) provides data for a correct estimation of
the events that take place

throughout the composting process 7.

Although several researchers 1 3 8 have studied the
dynamics of the microbial

communities, little is known about the relationship
between microbial diversity

and enzyme activities during composting of the organic
fraction of municipal

solid waste (MSW). The present work thus aims at
constructing a fuller picture

of the microbial and enzyme activities in a small-scale
composting system.

                                               In spite of many pitfalls
affiliated with C/N ratio, it is generally considered as an index of compost
maturity 8. Also for determining compost maturity a C/N ratio

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