(271d) Evaluation of Preliminary Adhesion Processes of Cyanobacteria (blue-green algae) on Photobioreactor Materials

Suvarna N L Talluri¹, Robb M Winter¹ and David R Salem^1,2

¹Department of Chemical and Biological Engineering

²Composites and Polymer Engineering (CAPE) Laboratory

South Dakota School of Mines & Technology, Rapid City, SD

Abstract

Due to increasing interest in replacing fossil fuels with biomass based fuels, cyanobacteria are considered as an attractive third generation renewable feed stock for biofuel production for their advantages such as CO₂ fixation, use of sunlight, waste water treatment and ease of genetic engineering. In spite of growing demand and valuable biofuels being already produced by cyanobacteria, their cultivation in photobioreactors (PBRs) poses a number of problems one of which is their tendency to cause rapid biofouling of PBR materials. Cyanobacteria fouling on PBR materials can be a significant operating challenge that can decrease the overall biofuel productivity of the system by interfering with the light penetration to cyanobacteria cells. Despite the fact that cyanobacteria are a common group of microorganisms that cause fouling in photobioreactors, studies focused on prevention of cyanobacteria are scarce. A detailed understanding of the adhesion strategies of cyanobacteria on PBR materials is needed in order to successfully develop antifouling materials. Therefore, in this study, we investigated the preliminary adhesion processes of a selected cyanobacterium (genetically engineered to enhance biofuel production) on a range of existing or potential PBR material surfaces. This was done by evaluating the physicochemical changes occurring during the initial adhesion and biofilm development of the cyanobacteria. Experimental techniques such as surface contact angle measurements, bright field microscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and atomic force microscopy (AFM) were used to characterize the adhesion processes of cyanobacteria on the PBR materials. Contact angle measurements revealed that surface hydrophobicity/hydrophilicity of PBR materials was altered within 12h due to the formation of conditioning films. Atomic force microscopy revealed that changes in surface roughness, surface height and thickness of the conditioning films were substrate specific. ATR-FTIR spectroscopy showed that proteins and polysaccharides were the dominant groups involved in adhesion of the genetically engineered cyanobacteria to the PBR materials.

Keywords: Biofouling, photobioreactors, cyanobacteria, adhesion mechanisms.