Advancement of biosurfactant production and biosurfactant-aided pollution remediation

Zhu, Zhiwen (2018) Advancement of biosurfactant production and biosurfactant-aided pollution remediation. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Biosurfactant enhanced soil washing and/or bioremediation have been proven as promising technologies for cleaning up petroleum hydrocarbon contaminants (PHCs)- and heavy metals- contaminated soil and groundwater. As environmentally friendly amphiphiles, biosurfactants display promising wetting, solubilization, and emulsification properties. Biosurfactant addition can enhance the mobility and bioavailability of entrapped PHCs in porous media, and finally improve their removal. Biosurfactants can also reduce the heavy metal toxicity and assist their removal through acting as metal complexing agents. The availability of economic biosurfactants, however, has become a major obstacle to their applications. In addition, little research has been conducted to investigate the role of biosurfactants, especially lipopeptides, in contaminated subsurface cleanup process and their impacts on oil degrading microbes. To fill the knowledge gaps, a number of methodologies and mechanisms aimed at economical biosurfactant production and advanced biosurfactant enhanced subsurface co-contamination control have been investigated. Economical lipopeptide production by Bacillus Substilis N3-1P using fish waste as an unconventional medium was achieved. The lipopeptide production was further enhanced using immobilized robust biocatalysts on porous fly ash by Bacillus Substilis N3-1P, and the associated mechanisms were explored. The lipopeptide production by Bacillus Substilis N3-4P was optimized and its application for crude oil removal was examined. The impact of the generated biosurfactant on the biodegradation of PHCs in presence of heavy metals was finally evaluated. The newly developed lipopeptide production methodologies and the associated mechanisms helped to break down the barriers impeding economical biosurfactant production. The research outcomes (e.g., fish-waste-based hydrolysate, fly ash (FA) - based robust biocatalyst and optimized growth medium) could contribute to a cost-efficient biosurfactant production through proper selection of waste materials, advanced bioreactor design and medium optimization. This dissertation research was also a first attempt to identify the role of lipopeptides in cell surface associated biodegradation mechanisms in a co-contaminated environment. This research could help implement effective soil and groundwater remediation practices and bring short/long-term benefits to the governments, industries and communities at regional, national and international levels.

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