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Discoveries in Agriculture and Food Sciences - Vol. 11, No. 3
Publication Date: June 25, 2023
DOI:10.14738/dafs.113.14605.
Bhattacharya, S. (2023). Organic Matter Decomposition: A View on The Fate of Lignocellulosic Materials. Discoveries in Agriculture
and Food Sciences, 11(3). 22-31.
Services for Science and Education – United Kingdom
Organic Matter Decomposition: A View on The Fate of
Lignocellulosic Materials
Susinjan Bhattacharya
School of Agriculture and Allied Sciences,
The Neotia University, Sarisa, West Bengal, India
ABSTRACT
Organic matter decomposition, a complex process with all the physico-chemical and
biological factors leads to breakdown of organic residues. The prime role in this
process is played by microorganisms with their enzymes. The process is beneficial
not only to generate matters of soil fertility enhancement, but also it can lead to the
products that can add value to soil. Slow and difficult matters to be decomposed like
lingo-cellulosic materials can also be subjected to this decomposition process for
the generation of not only new and beneficial microflora, but also products of value.
The present work discusses here in brief the process of organic matter
decomposition and its importance in rice straw breakdown and lignocellulosic
material decomposition.
Keywords: Decomposition, Factors in decomposition, Microorganisms, Enzymes,
Lignocellulose
INTRODUCTION
Decomposition as a complex process involves physico-chemical and biological factors to
breakdown the raw materials to a usable simpler form of substance and usable as a soil
amendment called as manure. There are two ways for the process of decomposition: aerobic
(in presence of oxygen) and anaerobic (in absence of oxygen). Microorganisms play a bigger
role in decomposition. [Texas A&M Agrilife Extension, 2023; UtahState University, 2023]. The
common subjects for decomposition are waste matters. With regard to the ability of the
substrates to undergo decomposition, the different categories are: easily decomposable,
difficult to decompose, recalcitrant to decompose. Waste, discarded and useless materials
without any value can be either solid, liquid, or mixed in nature. Nonbiodegradable wastes,
mainly are synthetic in nature and are difficult to decompose. The alternate option with
nonbiodegradable wastes is to subject them for recycling preceded by seperation of their
elements [Bhansali, 2021; Lee 2018; Singh, 2021; Tigtag, 2023]. The present work discusses
here in brief the process of organic matter decomposition and its importance in rice straw
breakdown and lignocellulosic material decomposition.
ORGANIC MATTER DECOMPOSITION
The breakdown of organic molecules is an important contributor to the ecosystem respiration
and recycler of energy and nutrients in the ecosystem. The process along with the process of
photosynthesis controls net carbon emission form the ecosystems. The process involves
biochemical transformation in breakdown of complex substrates to the simpler forms [Ravn et
al., 2020; Smith and Smith, 2012]. The dead plant remains in soil or plant litter is mineralized
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Bhattacharya, S. (2023). Organic Matter Decomposition: A View on The Fate of Lignocellulosic Materials. Discoveries in Agriculture and Food Sciences,
11(3). 22-31.
URL: http://dx.doi.org/10.14738/dafs.113.14605
and transformed to organic matter through the activities of soil microorganisms. Conversion of
litter to organic matter involves many steps including the site and soil characteristics. Roots
and Arbuscular Mycorrhizal fungi (AM) fungi are one of the key players in litter decomposition.
These contributes to lignin, melanin and glycoproteins as the prime constituents. Litter
transformation occurs along a gradient from above ground soil to the below ground soil,
wherein aboveground litter is converted to humus [Prescott and Vesterdal, 2021]. Herein, the
rate of decomposition of leaf tissue happens faster than the stem or wood decomposition
[Middleton, 2020]. However, the climate plays a crucial role in litter decomposition [Joly et al.,
2023]. Light is a vital factor in semi-arid ecosystems to lead litter decomposition [Austin and
Vivanco, 2006]. The rate and course of litter decomposition influences biomass, nutrient and
physico-chemical properties of the soil [Kumar et al., 2010].
ROTTING, FERMENTATION AND DECOMPOSITION: DIFFERENCES INVOLVED
Decomposition, a term related to ecology is a process of microbial digestion and destruction of
dead material by the microbial process. Fermentation, a metabolic process and controlled
process of decomposition as well as a microbial process dependent on enzymes varies with in
composition of the involved enzymes to those of decomposition process involved enzymes
[Surstromming, 2023]. In contrast, rotting, a state of decaying is an uncontrolled act of
decomposition [Fermenters kitchen, 2023; Lakna, 2022]. The process of composting involves
decomposition, and fermentation or putrefaction (anaerobic process) is an alternative
suggestive to the process of composting (aerobic process) [Feed Innovation Services, 2013;
Merfield, 2013; Organko, 2022; Chesapeake Bay Foundation, 2023; BioBag International AS,
2023].
FACTORS INVOLVED
Physico-Chemical
Composting, a process is dependent upon different factors, like microbial composition and
succession, particle size and surface area of the particle, moisture content, aeration,
temperature, volume of the material, C:N ratio, pH, etc. [Master Gardener, 2023; Nsimbe et al.,
2018; Meena et al., 2021].
Substrate
Substrate quality depends upon the rate of microbial activity in organic matter decomposition.
Flow of C and N to silt and clay fractions depends on the quality of substrate. The process leads
to increased C and N residence times [Cyle et al., 2016]. Rate of decomposition reduces with
ageing of litter and dead plant, animal residues and other substrates are decomposed till the
point wherein they are no more recognizable and referred to at that stage as soil organic matter.
The process of litter decomposition depends upon the interlinked action of three driving
variables: physico-chemical environment, resource quality and decomposer organisms. [Doe
and Johnson, 2009; Cotrufo et al., 2010]. Furthermore, administration of antibiotic alternatives
in decomposition leads to a change in litter bacterial flora, and elevate the abundance of
beneficial bacteria and reduce pathogen prevalence [Pedroso et al., 2014]. The other important
factor that plays role in decomposition is climate [Joly et al., 2023]. In contrast, soil organic
matter can be protected from decomposition physically and chemically. Additionally, low
temperature and C: N ratio, lesser number of decomposers apart from large scale spatial
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separation brings down the rate of decomposition [Nivethadevi et al., 2021]. Activity of extra- cellular enzymes in organic matter decomposition depends on substrate quantity and
availability. Variation in enzymes is also an important factor here. Substrate affinity of enzymes
varies with the temperature sensitivity for polymer hydrolysis and monomer oxidation
[Myachina and Blagodatskaya, 2015]. In shrub ecosystems, effect of nitrogen addition in litter
decomposition remains neutral due to the effect of low temperature and phosphorus limitation.
Additionally, exogenous nitrogen inhibits lignin degradation but promotes breakdown of
readily decomposed litter components [Zhang et al., 2021].
In a summary, substrate availability and decomposer community limits organic matter
breakdown [Wutzler and Reichstein, 2008]. Oxidation of the carbon compounds provides
energy to the decomposers. Breakdown of organic matter is a crucial requirement for energy
and nutrient cycling in the ecosystem food web as well as contributor to the ecosystem
respiration [Ravn et al., 2020; Middleton, 2020]. With the increase in recalcitrant chemical
components in the litter, decomposability rate of litter decreases, and the decrease in
decomposability or substrate quality is a complex process involving direct chemical changes in
the substrate itself and microbial succession in biochemical reactions. Once, the limit value in
decomposition is reached, the process will be proceeding towards a more stabilized soil organic
matter. Thus, at higher initial nitrogen concentrations, C/N ratio comes down, least amount of
organic matter is left over, indicating a stage of stabilized soil organic matter, low
decomposition rate and lower mass loss [BERG, 2000]. Substrates vary with regard to their ease
of decomposition, and in the scale from very rapid decomposable to slow decomposable,
substrates are: (i) sugars, starches and simple proteins, (ii) crude proteins, (iii) hemicelluloses,
(iv) celluloses, (v) fat, waxes, resins, (vi) lignin [Musa, 2023]. Shrub litter decomposes than the
tree litter [Carnevale and Pablo, 2001] [25]. However, breakdown of organic matter helps in
release of nutrients and functioning of the food web [FAO, 2023]. Additionally, climate
indirectly affects litter decomposition by interacting with plant physiology and plant
resorption, affecting chemical composition of the litter at its formative stages [Suseela, 2019].
Quality and quantity of the litter defines ecosystem functioning which inturn depends on plant
species, forest structures, seasons and climate factors apart from soil drainage [Giweta, 2020;
Schnecker et al., 2019; Krishna and Mohan, 2017; Certini et al., 2015; Kumar et al., 2010].
Biological: Enzymes & Microorganisms
The process of composting involves both aerobic and anaerobic microorganisms [FAO, 2023].
There is also involvement of thermophilic bacteria, fungi and actinomycetes [Joseph, 2019].
Thermophilic bacteria succeed mesophilic bacteria. Actinomycetes plays role in breakdown of
materials like newspaper, bark, and other lingo-cellulosic materials. Apart from actinomycetes,
mould and yeasts also help in breakdown of lingo-cellulosic materials. Additionally, protozoa
consume inactive bacteria, fungi and actinomycetes. There are other physical decomposers also
which feed on the organic waste [Editors, 2022]. Furthermore, there are different kinds of
enzymes, like cellulases, hemicellulases, ligininase, chitinases and esterases, etc. with varied
activities that play a role in composting [Finore et al., 2023; Nakamura et al., 2004; Murugesan
and Amarnath, 2020; Infinita Biotech]. Lignin modifying enzymes from different producers acts
at the compost maturity stage [Robledo-Mahon, 2020]. These activities lead to a change in
concentrations of minerals in compost [Bohacz, 2019]. The mesophilic stage also has the
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Bhattacharya, S. (2023). Organic Matter Decomposition: A View on The Fate of Lignocellulosic Materials. Discoveries in Agriculture and Food Sciences,
11(3). 22-31.
URL: http://dx.doi.org/10.14738/dafs.113.14605
presence of bacteroides and proteobacteria as the dominant flora apart from the presence of
bacteria, fungi, etc. [Biyada et al., 2021; Li et al., 2019; Rath et al., 2022].
BREAKDOWN OF LIGNOCELLULOSIC MATERIALS
Lignocellulose, component of a waste biomass breaks down when acted upon by the
lignocellulose-degrading enzymes; cellulases, hemicellulases, laccases and ligninases [Chandra
and Madakka, 2019]. Lignocellulosic material consists of cellulose, hemicellulose and lignin,
wherein cellulose is a homopolymer of glucose residues, and lignin is a complex polymer of
phenylpropane [Sahay, 2022]. The main source of lignocellulosic materials is plant biomass,
and apart from fungi as the primary degraders, bacteria also play an important role as the
potential degraders [deSouza, 2013; Wilhelm et al., 2019]. Lignocelluloses also act as a matrix
wherein enzymatic hydrolysis for biofuel production occurs [Baig, 2020]. Microbial synergistic
consortia of a thermophilic filamentous fungus and thermophilic actinobacterium has been
reported to act as lignocelluose degraders [Shi et al., 2020]. Pretreatment of lignocellulosic
materials also plays role in generation of fermentable sugars [Kucharska et al., 2018]. The best
degraders of lignin in nature are the basidiomycetes white-rot fungi, followed by the brown rot
fungi. Enzymes that play role in the lignin breakdown are namely, laccases, manganese- dependent peroxidases (MnP), lignin peroxidases (LiP), and versatile peroxidases (VP) [Andlar
et al., 2018]. A complex bacterial consortium with species of Actinobacteria, Proteobacteria,
bacilli, Sphingobacteria, and Flavobacteria in an enrichment culture system has been seen to
breakdown different forms of lignocellulose [Georgiadou et al., 2021]. Furthermore, soil
invertebrates also play a role in lignocellulose breakdown [Bredon et al., 2018]. The complex
structure of lignocellulose needs participation and interaction of a variety of microorganisms.
This also highlights upon the importance of conducting more research to elucidate the
collaborative degradation mechanisms [Zhu et al., 2021].
BENEFITS OF ORGANIC MATTER DECOMPOSITION
Organic matter decomposition leads not only to the formation of humus, but also provides
compost that improves soil structure, add plant nutrients and beneficial microorganisms to the
soil. Addition of antibiotic, or antibiotic alternative helps to enrich beneficial microbes in the
litter and compost [Pedroso et al., 2014]. Long term administration of compost to soil helps in
improving the soil structure. Rice straw rich in ligno-cellulose when subjected to composting
improves not only the microbial diversity, but also the grain yield and grain quality [Huang et
al., 2023]. Paddy straw when left over in the field can neither be used as food or feed, but can
be composted to generate a compost of better quality as well as return back of nutrients to the
field [Nghi et al., 2020; Singh et al., 1995]. This helps also in generation of effective
lignocellulose degraders [Goyal and Sindhu, 2011; Shruti et al., 2015]. Lignocellulosic biomass
upon degradation leads also to the generation of high value products [Cecilia et al., 2021].
CONCLUSION
Organic matter decomposition involves the stages of: photo-oxidation, leaching, comminution
and mineralization and depends on a number of interacting processes [Schowalter, 2016;
Wantzen et al., 2008]. Composting is a process that speeds up the natural process of
decomposition in presence of microorganisms [Albright and Martiny, 2018]. Paddy straw
composting not only increases microbial activity and rate of composting but also improves the
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degrading microflora [Jusoh et al., 2013, Nghi et al., 2020; Huang et al., 2023]. Enrichment of
the process with cellulolytic bacteria in paddy cultivation led to an improved and better rice
yield [Lestari et al., 2020]. The process of organic matter decomposition is understood
experimentally from the view point of composting and humus formation. Thus, composting as
a process highlights also upon the discovery of more efficient lignocellulose degraders, apart
from helping to improve the soil quality and enrich the soil with beneficial nutrients and
microflora.
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