Brian Johnston

After arriving at SINTEF (Trondheim, Norway) I was taken on a tour of the facilities, which included the university grounds, a large 50 litre bioreactor, molecular biology labs, incubators and analytical chemistry devices (figure 1). I was introduced to many of the staff working in the offices and I was assigned an office area.  

When I began working with my BRISK2 partner, we planned the most effective use of my 2 week placement in detail. In the first week I prepared media for 6 simultaneous fermentations (a scaled-up version of some of my PhD thesis work) using waste polyethylene plastics as an addition carbon source for microbes to metabolise into biodegradable plastics (figure 2). Going from 250 ml to 1 litre fermentations illustrated some of the industrial difficulties my process would encounter in the real world. Working with the team at SINTEF, I was able to overcome some scale-up problems, such as emulsifying the waste plastics (which were in a hydrophobic wax-state of varying acid number) using ultra-sonification of the waxes preheated in a water-bath (figure 3). In the second week, we attempted replacing the nitrogen-rich media we used previously, with a lower-cost media that was used by SINTEF a number of years ago with a similar bacterial strain. This media was not successful at generating a high yield of biomass in the fermentations with the waxes added, but using periodic injections of glucose, fructose and other carbon sources in the control reactor, we were able to develop further plans of what to include in an alternative growth medium to tryptic soy broth (a soybean-casein digest microbial feed) that I am currently using.   

Over the 2 weeks, 12 fermentations were conducted with no contamination in any of the vessels or during the counting process, highlighting the high standard of the methodology used at the institute (figure 4). All of these techniques I can now apply to the remainder of my studies and during any demonstrations or lectures. Some of the supernatant left over from harvesting the cellular product has been stored at SINTEF which can potentially be analysed further by LC-MS against known standards if required (figure 5). The biomass generated was freeze-dried and is currently on route from SINTEF to my university laboratory for extraction and chemical analysis using GC-MS, FTIR, ESI-MS and GPC. After this analysis is complete we will know which biopolymers were produced and if there was any variance in their molecular structures (PHB/PHBV) due to the changes in acid number (number of ketone/aldehyde groups) of the waxes.  

The overall experience, courtesy of BRISK2, was extremely positive and I was able to generate far more data (CO2 levels, pH changes, LC-MS comparison, cellular respiration and alternative media) about the fermentation of my polyethylene waxes in 2 weeks than I would have been able to do otherwise (figure 6). I have also made some good academic links for further consultation and friends at SINTEF which I will stay in contact with (figure 7).