Microbial biosurfactants : is mainstream on the horizon?

Microbial biosurfactants have been holding the promise as environmentally friendly alternatives for petrochemical derived surfactants for the last decade. Indeed, across the market (large) companies are investing in these technologies and microbial biosurfactants are already applied in quite some consumer products today. The remaining hurdles for these technologies to really lift off can be summarized as high costs in comparison to the market references and a limited variety in molecular structures to satisfy the plethora of sought for functionalities. Moreover, most of the technologies are still in their infancy, characterized by suboptimal processes often resulting in batch to batch variation, a lack of knowledge and a of scale up evidence. A last issue is the fact that the use of so-called first-generation renewable substrates, such as sugar and vegetable oil, as substrates negatively impacts the LCA for microbial biosurfactants. At BBEPP and InBio.be we focus on all the above-mentioned shortcomings and aim to increase the microbial biosurfactant market segment in the coming years. We apply an integrated approach where microbial strain engineering, process (fermentation and purification) development and -optimization, scale up and application testing are tightly linked and interconnected. We recently succeeded in the development of a battery of Starmerella bombicola yeast strains producing a library of over 20 (new-to-nature) glycolipid biosurfactants and developed sustainable and scalable (continuous) fermentation and purification processes for these biosurfactants. The biosurfactants were screened in high throughput for a range of relevant properties for the industry, such as foaming, rheology, surface tension (and CMC), emulsification, but also biological properties such as anti-microbial and -viral properties. Moreover, efforts were done to develop the bioprocesses starting from waste- and side streams instead of 1G substrates, thus positively impacting the environmental impact of the new microbial biosurfactants. The combination of the described efforts is expected to result in a commercial breakthrough of microbial biosurfactant in the next ten years

Minimizing acetate formation in E. coli fermentations

Escherichia coli remains the best established production organisms in industrial biotechnology. However, during aerobic fermentation runs at high growth rates, considerable amounts of acetate are accumulated as by-product. This by-product has negative effects on growth and protein production. Over the last 20 years, substantial research efforts have been spent to reduce acetate accumulation during aerobic growth of E. coli on glucose. From the onset it was clear that this quest should not be a simple nor uncomplicated one. Simple deletion of the acetate pathway, reduced the acetate accumulation, but instead other by-products were formed. This minireview gives a clear outline of these research efforts and the outcome of them, including bioprocess level approaches and genetic approaches. Recently, the latter seems to have some promising results

Transport kinetics of ectoine, an osmolyte produced by Brevibacterium epidermis

Brevibacterium epidermis DSM 20659 is a halotolerant Gram-positive bacterium which can synthesize the osmolyte, ectoine, but prefers to take it up from its environment. The present study revealed that B. epidermis is equipped with at least one transport system for ectoine, with a maximal transport velocity of 15.7 +/- 4.3 nmol/g CDW center dot min. The transport requires energy (ATP) and is completely inhibited by the proton uncoupler, CCCP. The ectoine uptake system is constitutively expressed at a basal level of activity and its activity is immediately 10-fold increased by hyper-osmotic stress. Initial uptake rates are not influenced by the intensity of the hyper-osmotic shock but the duration of the increased activity of the uptake system could be directly related to the osmotic strength of the assay solution. Competition assays indicate that betaine, but not proline, is also transported by the ectoine uptake system