Physical and Biological Properties of Glycolipids and Bacterial Cellulose

Abstract

This thesis includes bioproduction, characterization, development, application and mechanism studies of two biomaterials/bioproducts, bacterial cellulose (BC) and sophorolipids (SLs). The thesis seeks to introduce bioproducts to novel applications, by investigating the principles or mechanisms behind and optimizing the performance or activity. In the first part, we have established a facile and effective bioproduction method for ultra-thin bacterial cellulose mats with predictable thickness at nanometer scale. The BC mat was designed for new optical applications, including transparent fiber substrate providing large surface area, and antireflection coating (ARC) on silicon wafer which demonstrated broadband, interference type antireflection property. The ultra-thin BC was further modified by trihexylsilylation to achieve hydrophobicity, which is essential for silicon solar cell ARC outdoor. The discipline behind was investigated on thickness and density gradient (orientation of BC mat). In the second part of the thesis, a new family of sophorolipid derivatives with diversified structure was studied for their potential as antimicrobial agents. Structure-activity relationship and membrane depolarization study was carried out on different chain length and acetylation degree. Other than single drug therapy, one of the sophorolipids, SL hexyl ester, was designed for multidrug therapy in combination with antimicrobial peptides. This approach effectively potentiates and broadens the spectrum of antimicrobial peptide. The knowledge of synergy mechanism was studied, which contributes to the rational design of novel therapies combating resistance, and against persister cells. The thesis also provides strategies and concept for future directions.

Bioproducts have been gaining increasing interest in the sustainable industrial society, to shift the dependence to renewable sources (energy goal) and established a biobased industry (economic goal). Due to evolutionary pressures, many of them exhibit superior properties, such as biocompatibility, biodegradability, low-ecotoxicity, and privileged structures targeting proteins with selectivity. Microorganism based bioproduction provides the phethora for metabolic pathways that allowing multistep reaction happens at a mild condition. Thus it has been well studied and successfully brought to many industry fields. Such phethora also allows tools like metabolic engineering to adapt microorganisms to meet technical constraint, and manipulate product structures.