Production and characterization of polyhydroxyalkanoates (PHA) from corn silage using Thermus thermophilus HB8

Submitted in fulfillment of the academic requirement of the degree of Masters of Applied Science, Chemistry: Durban University of Technology, Durban, South Africa, 2019.In this study, a biodegradable copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was produced from an agricultural by-product namely corn silage through a fermentation process using Thermus thermophilus HB8. Two types of corn silage pre-treatment processes viz. deionized water treatment (unhydrolysed) and acid hydrolysis were carried out at different loadings of corn silage (6%, 12%, 24% and 48% m/v), at 70°C for 50 h. Both pre-treatments were able to produce biopolymer where 6%, 12%, 24% and 48% unhydrolyse pre-treatment yielded 12%, 20.44%, 28.42% and 18.65% PHA, respectively; 6%, 12%, 24% and 48% acidic pre-treatment yielded 42.23%, 49.53%, 56,41% and 61.32% PHA, respectively. The extracted polymer was characterized by Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectroscopy (UV-Vis) to study the characteristic bands; gas chromatography was used to identify the PHA monomers of the extracted methyl esters; scanning electron microscopy (SEM) was used to study the morphology of the bioplastic products; tensile testing was used to study the tensile properties of the bioplastics.

Extraction of pesticides using selected analytical methods from soil and maize segments : cumulative and health risks assessment.

Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.Increased agricultural operations result in increased usage of various pesticides to safeguard agricultural crops, however this is done without paying attention to the effects of the amounting potential harm both humans and the environment are exposed to. In this present study, a structured study was conducted to investigate the uptake of atrazine, mesotrione, 2,4- dichlorophenoxyacetic acid and glyphosate herbicides from contaminated soil and their translocation into different maize segments. Soil profile and quality of irrigation water were also assessed as they are crucial resources required in agricultural crop production due to their ability to influence the yield and quality of the agricultural products. Various physicochemical parameters were measured in an attempt to monitor the soil profile, irrigation water and maize quality harvested from Buhle farm located in Howick, KwaZulu-Natal Province. The irrigation water physicochemical parameters considered were the pH, electrical conductivity, alkalinity and chloride concentration. The soil physicochemical parameters considered were moisture content, pH, electrical conductivity, texture, total nitrogen as well Mg, Na, K, Zn, Mn, P and N elements. Maize was analysed for nutrition content and medicinal health promoting compounds. Based on the attained results, the soil texture contained high clay content (56.4%), followed by sand (40.6%) and silt (2.98%). The concentrations for total nitrogen, phosphorus and potassium which were translated to high soil fertility were 2700, 19 and 222 mg L-1, respectively. These particular elements are essential for agricultural plantation processes and consequently maize quality and maize yield. The levels of sodium, sodium adsorption ratio and electrical conductivity found in irrigation water were 0.05 mg L-1, 2 and 1.81 μS m-1, respectively. The findings showed that maize harvested from Buhle farm had high starch content of 58.6%. Fibre, protein and fat contents in maize were 23.4, 9.01 and 4.55%, respectively. Furthermore, the total anthocyanin, total flavonoids and total phenolic acid content were 8.5, 49.5 and 100 mg L-1, respectively. High amounts of phenolic acid detected indicated therapeutic ability of the maize since phenolic acids are essential for cancer prevention to the consumer. The presence of anthocyanin, flavonols and phenolic acids in maize crop is associated with its quality that could benefit livestock and human after consumption. The analysis of herbicides in soil and maize samples require sample pre-treatment due to their low concentration and complex matrix hence an ultrasonic extraction, microwave-assisted extraction (MAE), Soxhlet extraction (SE) and QuEChERS methods were investigated. The optimization and application of ultrasonic extraction, MAE, SE and QuEChERS methods were conducted for the effective extraction of pesticides from maize and their corresponding soil samples. The analysis of pesticides (atrazine, glyphosate, 2,4-dichlorophenoxyacetic acid and mesotrione) was done with gas chromatography-flame ionization detector. Factors influencing the efficiency of the extraction methods such as the extraction solvent, extraction time, solvent volume, sample wetting and spiking concentration were assessed. Under the optimum experimental conditions, the relative standard deviation (RSD), coefficient of determination (R2), limit of detection (LOD), limit of quantification (LOQ), and percentage recoveries were the quantitative characteristics of the current methods assessed. All calibration curves showed a high correlation coefficient (R2) ≥0.996, indicating good linearity. The LODs and LOQs ranged between 0.22-0.32 μg L-1 and 2.0-2.9 μg L-1 for SE , 0.1-0.25 μg L-1 and 1.1-2.2 μg L- 1 for MAE, 0.02 – 0.15 μg L-1 and 0.2 - 0.5 μg L-1 for UE and 0.01 – 0.23 μg L-1 and 0.13 – 0.8 μg L-1 for QuEChERS. The maize and soil analytes recoveries for SE, MAE, EU and QuEChERS ranged between 62-80% and 70-81%, 80-98% and 85-101%, 100-104% and 91- 97 % and 94-115% and 92-101%, respectively with the repeatability, articulated as RSD values of which are within the acceptable range as they are lower than 20%. MAE method showed higher sensitivity compared to SE while, UE and QuEChERS both showed high sensitivity for the extraction and quantification of the target analytes at low concentrations found in soil and maize cob. It was observed that 2,4-dichlorophenoxyacetic acid (2.4-D) was least absorbed by the soil, however, all the studied herbicides showed high absorption in the leafy segment of the maize plant due to the high polarity of the leaf cuticle. Glyphosate showed high absorption rate in soil, roots, stalk and leaves while mesotrione was highly absorbed in corn and tassels in all treatments. The absorption rate of analyte increased with increasing growth days. The higher treatment concentration (0.75 g L-1) showed elevated accumulation with the highest concentration (1.02 μg L-1) observed for glyphosate in leaves after 140 days and high mesotrione in corn (0.51 μg L-1) and tassel (0.42 μg L-1) observed after 120 days. Even though all maize treatment showed a pesticide toxicity index (PTI) values of <1, the health risk index (HI) data were below 100% threshold as well indicating no possible health risk linked with the intake of these crops by both adults and children

The Effect of Peeling and Boiling Process on Nutrition and Health-Promoting Compounds of Root Vegetables Harvested at Mjindi area Located in Jozini, KwaZulu Natal, South Africa

The effect of peeling and boiling process was investigated on nutrients and health-promoting compounds of amadumbe (Colocasia esculenta), carrots (Daucus carota), sweet potatoes (Ipomoea batatas) and potatoes (Solanum tuberosum). The results indicated that peeling and boiling led to significant reduction of nutrients (total soluble starch, total soluble protein, crude fibre) and health-promoting compounds (flavonols, anthocyanin and phenolic acid). Peeling effects on nutrient content did not yield similar outcome (increase and decrease). Carrots showed insignificant loss of total soluble starch after peeling and major loss was observed after boiling. Amadumbe shows substantial loss of fibre after peeling, peels yielding 42.38% and edible part yielding 8.31% compared to all of the analysed vegetables. Health-promoting compounds were reduced significantly peeling and boiling process. The nutrient and phytochemical compounds in the peels of the various vegetables depends on method of peeling. Fourier-Transform Infrared Spectroscopy (FT-IR) bands evidenced the presence of nutrients and health-promoting compounds in studied vegetables. Keywords: Boiling; Flavonols; Health promoting compounds; Nutrients; Peeling; Phenolic acid</jats:p

Production and characterization of polyhydroxyalkanoates (PHA) from corn silage using Thermus thermophilus HB8

In this study, a biodegradable copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was produced from an agricultural by-product namely corn silage through a fermentation process using Thermus thermophilus HB8. Two types of corn silage pre-treatment processes viz. deionized water treatment (unhydrolysed) and acid hydrolysis were carried out at different loadings of corn silage (6%, 12%, 24% and 48% m/v), at 70°C for 50 h. Both pre-treatments were able to produce biopolymer where 6%, 12%, 24% and 48% unhydrolyse pre-treatment yielded 12%, 20.44%, 28.42% and 18.65% PHA, respectively; 6%, 12%, 24% and 48% acidic pre-treatment yielded 42.23%, 49.53%, 56,41% and 61.32% PHA, respectively. The extracted polymer was characterized by Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectroscopy (UV-Vis) to study the characteristic bands; gas chromatography was used to identify the PHA monomers of the extracted methyl esters; scanning electron microscopy (SEM) was used to study the morphology of the bioplastic products; tensile testing was used to study the tensile properties of the bioplastics.</jats:p