First of all, I thank and praise God for His guidance and blessings throughout my final year project. Special appreciation and sincere gratitude goes to my supervisor, Dr. Nurlidia Mansor, for her guidance and support during the completion of my final year project in partial fulfillment of the requirement for Bachelor of Engineering (Hons) of Chemical Engineering. Studies of the degradation effect of the slow release have been found to be the least studied in the literature.
In order to understand this process, the current experiment is designed to study the physical and chemical characterization of biopolymer material degradation and subsequent urea release in wet (40% WHC) sterilized and unsterilized soil at different incubation periods. A spectrophotometer is used to quantify the biopolymer degradation and also the release of urea in the soil to achieve the objectives of the study. The study will understand the suitability of biopolymer based CRF for paddy soils and under different conditions over a period of time.
From the study it is noted that degradation had occurred and caused the change in the morphology of the coating. This proves that there is a relationship between enzyme activity, biopolymer degradation and urea release.
- Background Study
- Problem Statement
- Objectives of Study
- Scope of Study
However, studies on CRF that analyze the degradation of biopolymer coating over a period of time are rare. By understanding the biopolymer degradation with the presence of a specific element in the soil, we could improve and optimize the current CRF technology. This project also focuses on the degradation of the coating in wet soils, which is mainly used in rice fields.
Paddy field uses urea as its main fertilizer, and due to its wet and flooded cycles, large losses of urea to various gases create economic, plant yield and environmental problems. To study the material degradation of biopolymer in wet sterilized and unsterilized soil during different incubation periods. This study involves physical and chemical analysis for film and soil samples under two different soil treatments (sterilized and unsterilized) over different time periods.
In the study, wet soil is measured by determining the water holding capacity (WHC), where the value is approximately WHC). The use of sterilized and non-sterilized soil is intended to demonstrate the effect of the presence of microbes on biopolymer degradation.
Microbial activity in soil
On the other hand, a research paper by Jenkinson & Ladd (1981) mentioned that soil microbial biomass, a living part of soil organic matter, is a transformation agent for added and native organic matter and acts as a volatile reservoir for nitrogen available from plants. , phosphorus and sulfur. The steps in the degradation process are shown above which consist of two parts that occur simultaneously which are photodegradation and biodegradation. Photo degradation is caused by exposure to sunlight and also mechanical pressure from the ground.
Biodegradation is a chemical degradation of polymers due to the action of natural microorganisms that produce carbon dioxide and water. These two processes will eventually release the presence of urea in the soil layer. Immature or young plants have a higher nitrogen content, lower (C:N) ratios and faster decay of organic matter.
The amount, type and availability of the organic matter will determine the microbial population and how it develops. This is done to determine the effect of no microbes in the soil against degradation of the coating.
Urea
Biopolymer Coating
First, the enzyme for breaking down starch is readily found in the soil. According to Haiyan Sun et. 2008), crude starch digesting enzymes (RSDE) refer to enzymes that can act directly on crude starch granules below the gelatinization temperature of starch. In addition to that, the price of raw material for starch is also considerably cheap. 2004), starch-based materials have been of particular interest due to their generally low cost of starch.
According to Rose (1980), starch occurs in the form of water-insoluble granules as the main reserve carbohydrate in all higher plants. Thus, amylase can be divided into three groups: α-amylases (endoamylases), β-amylases (exo-amylases) and glucoamylases [Ajayi A and Fagade O. 2003)]. Figure 2 below shows the hydrolysis of starch by α - amylase enzymes.
- Soil collection/sampling
- Soil Sample Preparation
- Experiment Design
- Physical and Chemical Analysis
The soils are then put into bottles in which each bottle contains 50 g of the sample. Autoclaved soil is prepared by keeping the soil in an oven at 121oC and pressure at 0.1 kPa for 21 minutes [B. After the soil sample is prepared and incubated according to the settling time, a total of 20 samples should be analyzed (Table 3).
For each determined week, the sample is taken for physical and chemical analysis. Two experiments have been performed for physical analysis of the sample, namely Fourier Transformed Infrared-Attenuated Total Reflectance [RJ Cox PhDa (2000)] and also Field Emission Scanning Electron Microscopy (FESEM). Several experiments have been performed for chemical analysis of the sample, namely microbial biomass, carbon and nitrogen [Carol Grace et.
To perform the analysis of biomass carbon and nitrogen, the sample must use a gassing and extraction method. To determine urea N, pipette an aliquot of the extract containing urea N into a 50 ml volumetric flask, adjust the volume to 10 ml with a 2M KCl-PMA solution and add 30 ml of color reagent. Then transfer about 10 ml of this solution to a Klett-Summerson colorimeter tube and measure its red color intensity.
Calculate the urea-N content of the extract using a calibration graph plotted from the results obtained with standards. To prepare this graph, dilute 10 mL of standard urea N solution to 100 mL with 2 M KCl-PMA solutions in a volumetric flask and mix thoroughly. Adjust volumes to 10 ml by adding 2M KCl-PMA solution and proceed as described for urea N analysis of soil extract.
Pipette 0.1 mL of supernatant and make up the volume to 1 mL in each tube with water. To determine the linearity of the reaction with time, a 150 mL aliquot of the reaction mixture was withdrawn at defined intervals as described below. After centrifugation for 5 min at 14,000 rpm in a refrigerated bench centrifuge, a 30 mL aliquot of the clear supernatant of the stopped reaction was mixed with 300 mL of iodine reagent (0.0075% iodine and 0.075% KI).
- Fourier Transformed Infrared-Attenuated Total Reflectance (FTIR-ATR)
- Field Emission Scanning Electron Microscopy (FESEM)
- Urea Estimation
- Starch Determination
- Total Amylase Activity Determination
The morphological feature of biopolymer coating in both non-autoclaved and autoclaved soil after 7 weeks of burial was observed using Field Emission Electron Microscope (FESEM). The difference between both coatings can be easily detected at magnification 1000x as the surface of the biopolymer coating in non-autoclaved soil is rougher and contains more pores compared to autoclaved soil. On the other hand, FESEM analysis of the coating in autoclaved soil shows much clearer surface with a small amount of pores.
The reason for high porosity and rough surface in non-autoclaved soil is due to the structure of the layer that has been broken down and destroyed by microorganisms. From figure 8 it can be observed that the content of microbial carbon in non-autoclaved soil increases slightly from week 0 to week 3 and then starts to decrease. In non-autoclaved soil, it is found that there is not much difference for microbial carbon in autoclaved soil and it varies from 190 to 200 mg/ml.
To quantify the amount of urea in the soil, the standards are prepared and the spectrophotometer test is performed. The results of the test are as indicated in table 4 and figure 9. The concentration shows the values in micrograms of urea (μg). The quantification of urea in soil samples is then accomplished by interpolating the absorbance of the soil samples with the standard that has been prepared.
The absorbance data is used to calculate the equation and obtain the concentration of urea in the soil. The concentration of urea for each week is calculated from the average urea content of the original and replicate of the soil sample that has been prepared. From the graph, it could be observed that the starch content of autoclaved soil is higher than that of the non-autoclaved soil.
Degradation is expected to occur less in autoclaved soil, as the number of microbes in the soil is negligible once the soil has been sterilized. This trend can be roughly estimated to correspond to the curve of urea concentration in non-autoclaved soil (Figure 10). Enzyme activity increases in the first three weeks expected due to the growth of the microbes, which release the enzyme for degradation.
This trend shows small amounts of amylase activity as expected since there are no microbes in the non-autoclaved soil. From the graph it could be concluded that trend for enzyme activity can be roughly estimated to be similar to the curve for urea concentration in non-autoclaved soil.
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![Table 2 : Different Enzymes for Biopolymer degradation in soil [Z. Majeed et. al. (2012)]](https://thumb-ap.123doks.com/thumbv2/azpdforg/10248785.0/13.918.156.823.379.701/table-different-enzymes-biopolymer-degradation-soil-z-majeed.webp)
