MICROBIAL DEGRADATION OF PADDY STRAW Shailly, Aarohi Jain, Mandeep and Ranjana Bhatia Department of Biotechnology, UIET, Panjab University, Chandigarh-160014
RESULTS AND DISCUSSION
ABSTRACT The practice of burning paddy straw in areas like Punjab and Haryana to reduce the turn around time between harvesting and sowing for the second (winter) crop is a big concern for environmental pollution. In order to overcome this serious problem, non-hazardous and eco-friendly methods are required. This study is an attempt to assess the degradation of paddy straw using potential micro-flora.
Table 2 Determination of laccase activity
Figure 2 Concentration of reducing sugars in different treatments TREATMENTS Control 1(ST+H2O)
Different treatments involving urea, cow dung and soils from different sources were tested under in vitro conditions for efficient biodegradation of paddy straw. Results indicate that application of natural micro-flora present in cow dung in combination with 4% urea carries out effective degradation of paddy straw in a time duration of four weeks. Large populations of different microflora such as actinomycetes, phosphate solubilizers, nitrogen fixers and oligotrophs were found present during degradation. Thus, we report that microbial degradation of paddy straw is an efficient possibilities . Further analysis to quantify enhanced biodegradation is underway.
Control 2 (ST+H2O+UPT) Sample 1 (ST+CD) Sample 2 (ST+CD+UPT) Sample 3 (ST+Soil3+UPT)
ENZYME ACTIVITY (µM/min) DAY 20
DAY 40
0 0.072 0.4914 1.4346 0.3843
0 0.234 0.2853 1.253 0.6237
Maximum laccase activity was observed in S2(cow dung + urea pre-treatment) at day 20. This indicates that maximum lignin degradation happens after day 20 and was marginally reduce at day 40. The result
INTRODUCTION
supports the estimation of reducing sugars (Fig.2) and microbial diversity analysis (table 1).
Paddy straw is the most abundant and unutilized source of renewable biomass on the earth. Globally about 370 to 520 million tonnes of paddy straw is generated annually. In India, paddy is cultivated in about 43 million hectare producing about 96 million tonnes of rice and approximately 250 million tonnes of straw. As paddy straw is mainly composed of cellulose, hemicellulose, lignin and silica thus its decomposition process is difficult so as to reduce the turn around time between harvesting and sowing for the second (winter) crop, the management of residue is very important. There are many ways to do so, but due to different cost implications burning is the most favoured residue management practice in India. Burning paddy straw has various negative effects on the environment. It can cause a huge amount of nutrients loss from the soil, air pollution (one ton of paddy straw burning releases 3 kg particulate matter, 60 kg CO, 1460 kg CO2, 199 kg ash and 2 kg SO2), global climate change and also due to temperature rise during burning the soil dries up necessitating additional water for irrigation. Keeping this in mind the present study is done with the aim of degradation of paddy straw by microbial consortium to make the residue easier to manage and the recycled waste can be used to improves the soil fertility and health.
CONCLUSION Presence of reducing sugars indicates the degradation of paddy straw. The maximum concentration of reducing sugars was observed in treatment involving exposure of paddy straw to cow dung and urea after week 3(21 days).
Table 1 Analysis of microbial diversity in different treatments
Microbial population
Control 1 (ST+H2O) DAY 15
Total Bacteria
METHODOLOGY
Control 2 (ST+H2O+UPT)
DAY 25
DAY15
DAY 25
4×108 1.7×107 4×105
Nitrogen Fixers 1.6×108 1.6×109 1.1×104
Microbial samples : S1 - Soil from botanical garden Panjab University, S2 - Soil from agricultural field Ropar, S3 - Soil from sugar mill Ludhiana, CW - Cow dung from gowshala Chandigarh. Treatments: Control 1 - Only straw with water, Control 2 - Straw + Urea (4%) in Water, Sample1 - Straw + Cow Dung in Water, Sample 2 - Straw + Cow Dung + Urea (4%) in Water, Sample - Soil 3 + Urea (4%) in Water. Degradation analysis was done by estimating reducing sugars by DNSA method (Lee VJ et al. 2017) .
Estimation of microbial diversity was done by dilution plate technique.
Determination of laccase enzyme activity was done by colorimetric assay (Ferdeş M et al. 2018 ).
Fig 1 Treatment flask
Biodegradation of Paddy straw was successfully achieved upon pretreatment with urea for 24 hours and subsequent treatment with cow dung for four weeks. Substantial degradation was observed only after week 3. Role of different microbial populations and microbial enzymes was confirmed in the degradation process responsible. Therefore it is concluded that microbial degradation of paddy straw can be an efficient, sustainable and non-expensive alternative to stubble burning .
Phosphate Solublizers
9
Oligotrophs
UC
1.1×10 3.6×10
DAY 15
Sample 2 (ST+CD+UPT)
DAY 25
UC
4.2×108 1.6×109
UC
1.7×108
4
8
UC
DAY 15
Sample 3 (ST+Soil3+UPT)
DAY 25
DAY 15
3×106 1.8×109 3×107 3.9×108 4.2×104 1.1×109 1.6×104 5.1×108
6
6
9
1.2×109 3×105
1.3×108
UC = Uncountable
NG
-
4×108 -
1×107 1.2×109 1.5×108
NG
UC 2.4×106
8
9
1×109 2.7×106 1.7×108 UC
-
REFERENCES
DAY 25
UC 1×10 7×10 1×10 1.6×10 1×10 2.2×10 2.3×10 9 Actinomycetes 1×108 1.4×109 1.5×106 1.4×108 8.8×108 3.5×104 2.2×107 3.1×104 2×108 1.31×10 7 Fungi 1.1×108 2.6×109 5.6×108 UC 1.5×109 UC 1×109 Bacillus
7×10
8
Sample1 (ST+CD)
-
NG = No growth
The maximum population of microbes was observed in S2 (pre urea treated straw with cow dung) on day 25. On day 15 the microbial population in pre urea treated samples (Sample 2&3) was found to be less than control but recuperate on day 25, except fungi which were detected to flourished in the presence of urea .
Ferdeş M, Dincă M, Zăbavă B, Paraschiv G, Munteanu M, Ionescu M. Laccase enzyme production and biomass growth in liquid cultures of wood-degrading fungal strains. In46th International Conference “Actual Tasks on Agricultural Engineering 2018 Feb 27 (pp. 341-388). Lee VJ, Salimi MN, Yusoff A. Fermentable sugar production from paddy straw by two steps chemical pretreatment and hydrolysis process. InAIP Conference Proceedings 2017 Apr 26 (Vol. 1835, No. 1, p. 020009). AIP Publishing LLC. Matthews S, Kamal EA. Identification of rice straw degrading microbial consortium. Journal of Tropical Agriculture and Food Science. 2015 Jul 20;43:119-27. Vijayaprabhaka A, Nalliah Durairaj S, Vinoth Raj J. Effect of rice straw management options on soil available macro and micro nutrients in succeeding rice field. Intl J Chem Stud. 2017;5:410-3. Zhang X, Wang M, Wang R, Ma Z, Long D, Mao H, Wen J, Bernard LA, Beauchemin KA, Tan Z. Urea plus nitrate pretreatment of rice and wheat straws enhances degradation and reduces methane production in in vitro ruminal culture. Journal of the Science of Food and Agriculture. 2018 Nov;98 (14):5205-11.
ACKNOWLEDGEMENT Resources and opportunity provided by Department of Biotechnology UIET, Panjab University is greatly acknowledged .