Theses and dissertations (Applied Sciences)
Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/6
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Item A mucor circinelloides-based integrated biorefinery(2024-09) Zininga, Johnson Tungamirai; Permaul, Kugen; Singh, SurenABSTRACT The utilization of agro-based waste residue is a prominent example for establishing a circular bioeconomy. When agro-based waste is used to replace commercial growth media in microbial fermentation processes, it becomes expedient that the implementation of the biorefinery concept becomes integrated as the microbial biomass and their metabolites will add to the product spectrum. This study demonstrates an integrated approach towards valorization of sugarcane bagasse and microbial biomass comprising of Mucor circinelloides ZSKP. A maximum reducing sugar recovery of 80.67 g/l was achieved after combining lignocellulosic pretreatment with saccharification. A low temperature, glycerol and ammonium phosphate pretreatment method was established, where glycerol pretreatment conditions were reduced to 150°C and almost a third of the initial duration. This strategy will potentially result in lower energy consumption costs, decreased release of inhibitors and lower water consumption. The ammonium phosphate-containing hydrolysate yielded 12.89 g/l of fungal biomass after fermentation to add to 20.8 g lignin from the delignification step. Sequential fermentations were performed by addition of Saccharomyces cerevisiae as a co-culture to produce biomass and ethanol. The initial aerobic M. circinelloides fermentation was followed by mixed culture anaerobic fermentation. Fermentation of M. circinelloides (3 days aerobic growth) and S. cerevisiae (5 days of anaerobic growth) generated a balanced biomass yield of 17.9 g/l and ethanol yield of 18.69 g/l. Ethanol production demonstrated effective utilization of bagasse hydrolysate and offered the possibility of concurrent production with biodiesel in this biorefinery. The mixed biomass gave a lipid yield of (3.72 g/l) and a chitosan yield of (1.84 g/l), The lignin infused glycerol plasticized chitosan biocomposite plastic had a 100% improvement in thermogravimetric properties with almost 50% more energy needed to increase the temperature of the material when compared to glycerol-only-plasticized biocomposite. The deproteination step in chitosan extraction was modified and replaced with a protein recovery step, with protein yield being improved to a maximum of 187.89 mg/g. The amino acid composition of the protein showed that it has a relatively high content of lysine making it suitable as an animal feed supplement. This study presents strategies to address feasibility concerns for production of fungal chitosan, biodiesel and bioethanol from lignocellulosic waste and realizing the goal of a circular bioeconomy.Item Production of chitosan and lipids from a newly isolated Mucor circinelloides(2018) Zininga, Johnson Tungamirai; Permaul, Kugen; Singh, SurenFilamentous fungi are well-known sources of a wide variety of industrially-useful biomolecules. This study demonstrates the applicability of a newly isolated oleaginous fungi Mucor circinelloides ZSKP for lipid and chitosan production. Parameters affecting co-production were identified and were statistically optimized, which resulted in a 3–fold improvement in lipid production. The lipid profile showed a high content of unsaturated fatty acids including oleic, linolenic and linoleic acids, while palmitic acid was the major saturated fatty acid (21%). A comparative study to evaluate the efficacy of enzymatic and chemical treatments for biodiesel production from fungal lipids and sunflower oil revealed slightly enhanced production of biodiesel from fungal lipids, using a commercial lipase. The biodiesel synthesized using lipids from M. circinelloides ZSKP satisfied standard specifications and had a higher cetane number (56), lower kinematic viscosity (4.6 mm2/s) and lower acid number (0.03) compared to sunflower oil. Upon optimizing chitosan production and extraction processes the chitosan production was improved 2-fold. The fungal chitosan showed antimicrobial properties and was more effective against Aspergillus niger A chitosan spray was developed which was able to increase the shelf life of fresh fruit produce. These results indicate that Mucor circinelloides ZSKP is a promising candidate for concurrent production of lipids and the versatile bio-polymer chitosan.