M AT E R I A L S , OI L S & EN ER GI E S
BIOSURFACTANT ON THE RISE Dr Alexander Shulga, Head Scientest at Biotensidon, and his colleagues explain why, with industrially relevant volumes and pricing, rhamnolipids will become popular biosurfactants in the near future
hamnolipids are biosurfactants with excellent properties that partly outperform those of synthetic surfactants. Moreover, they are eco- and health-friendly. For many years, scientists have done extensive research on developing processing techniques that can ensure stable production at high volumes but, until recently, the results had not shown sufficient progress. Swiss-based Biotensidon International is the world’s first company to reach this stage of development and is now able to mass-produce high-quality rhamnolipids on an industrial scale. The company has already started an investment program that will see a full-scale, 2,000-ton capacity production site in Germany by the end of 2018. In 2019, production volume is to be expanded to reach 5,000 tons annually. Rhamnolipids are expected to gradually replace synthetic surfactants in a number of industry sectors.
Unique technology The technological breakthrough was achieved in 2016, by Biotensidon International’s fully-owned German subsidiary, which had started research on the industrial production of hamnolipids in 2011. Success was based on the correct setting of four main parameters: 1. An extremely robust non-GMO non-pathogenic wild strain of Pseudomonas aeruginosa 2. A team of experienced scientists and process technology experts 3. Generous funding by the company’s main investor 4. Choosing the right technological approach.
However, as well as pure rhamnolipids, Biotensidon also produces a rhamnolipids liquid (or powder) that leaves the initial production line, due to its multi-functional properties, which widen application potentials compared to those of pure rhamnolipids. It will be marketed under the trade name Rhapynal. Rhapynal is a natural supramolecular complex consisting of rhamnolipids (main component), polymer alginate and pigment pyoverdine. In the culture liquid Pseudomonas aeruginosa JRV-L rhamnolipid surfactants, alginate polymer and pigment pyoverdine form a supramolecular complex. This complex exhibits a high emulsifying, foaming activity, and greater biological effect if compared with purified rhamnolipids. Rhamnolipids are glycolipids that are synthesized by certain types of soil microorganisms, such as P aeruginosa strains. To date, about 60 different rhamnolipid congeners and homologs have been reported, as recently reviewed by Abdel-Mawgoud et al.1 P aeruginosa synthesizes a mixture of mono- and dirhamnolipids which consist of molecules of rhamnose and 3-oxidecanic acid (Figure 1) or other hydroxyacyl moieties mostly from C8 up to C12.
Figure 1 – Rhamnolipids from the bacterial strain P aeruginosa JRV-L Although listed last, the technological approach deserves some attention. Biotensidon has developed a new fed-batch fermentation technology that ensures Their low values of surface and interfacial tensions, as well as of critical stable output of rhamnolipids on an industrial scale (>30g/L) after 5 days micelle formation concentrations (CMC), indicate their high surface activity. of cultivation. One of the main problems of rhamnolipid production is The extracellular biopolymer also synthesized by the strain excessive foaming during fermentation. Both chemical and mechanical P aeruginosa JRV-L. It is a polysaccharide of an alginate nature methods can be used for foam destruction. However, chemical anti-foaming composed of β-l-guluronate residues and α-d-mannuronate residues agents can inhibit rhamnolipid biosynthesis and have negative effects on linked by β-1-4 glycosidic bonds with a molecular weight in the range downstream processes. On the other hand, conventional mechanical foam 3-4 x 105 Da (Figure 2). destructors cannot always cope with intensive foaming. The construction of Biotensidon’s bioreactors and the company’s unique foam-breaking methods prevent excessive foam formation and product losses, but at the same time ensure sufficient oxygen supply for optimum strain growth. Bacteria are cultivated in the mineral medium with glycerol as a carbon source. Glycerol, being a cheap byproduct of biodiesel production, contributes to the economic feasibility of Biotensidon’s technology. Its application allows reducing the costs of raw materials and provides less complex and Figure 2 – Extracellular biopolymer from the bacterial strain P aeruginosa JRV-L expensive isolation of end products from the culture liquid. Trace element solution is added periodically over the whole cultivation process. Pyoverdine, the third component of the complex, is a The downstream processes include: centrifugation, membrane greenish-yellow soluble pigment fluorescing in UV transmitted light. filtration, concentration by acidification, spray drying etc. Pyoverdine molecules consist of three structural-functional parts, represented with chromophore (dioxyquinoline nucleus), dicarboxylic Products and product properties acid (or its amide) and the peptide chain.2 Pyoverdine is characterized by The products that leave the initial production line are either a liquid high antioxidant activity. For instance, 50% inhibition of free radical concentrate with a rhamnolipids concentration of 100-400g/L, or a powder processes was observed in the presence of pyoverdine at the concentration with a rhamnolipids concentration of 750-800g/kg. 25µg/mL, and a maximum level (about 90%) – at 90µg/mL, which is Further purification processes lead to a powder with a rhamnolipids comparable with the action of melanin and other polyphenols. purity of up to 98%, depending on the desired application. Such highly Depending on the nutrient medium composition the strain P aeruginosa purified products will likely be used for pharmaceuticals, or possibly for JRV-L synthesizes from 70 to 700mg/l of pyoverdine. some forms of cosmetics products.
64 Speciality Chemicals Magazine 37.03 June 2017