68 SUSTAINABILITY With the aim of replacing petroleum
isododecane, the company Global Bioenergies has developed a process for obtaining a petroleum-identical but totally bio-based twin.14
The process is based on the use of a
mutated enzyme from a GMO.15, 16 The raw material used during fermentation is
a sugar syrup rich in glucose. The fermentation reaction in the presence of the modified microorganism leads to isobutene (Figure 4), a petrochemical platform olefin as it is the synthesis intermediate for many molecules of interest such as isododecane, isohexadecane and polybutenes, all of which are widely used in cosmetics (Figure 5). The fermentation yield by mass announced by
Global Bioenergies remains relatively low (25%) compared to conventional chemical processes. The atomic saving is close to 30%. It can be noted that these values are significantly lower than those for vegetable oil alkanes (Table 1). It is important to underline that branched
alkanes are hyper-recalcitrant to biodegradation unlike linear C11-C21 alkanes.8
Also, the real
biodegradability as well as the ecotoxicity of branched alkanes, relatively old substances, would deserve to be re-evaluated according to the current standardised methods, in order to optimise the choice of raw materials used in cosmetic products, in particular rinsed.
Biotechnological hemisqualane and squalane Hemisqualane is a linear and branched alkane consisting of 15 carbon atoms. It is a compound that does not exist in its natural state. Hemisqualane and squalane are therefore derived from synthetic biology and obtained from cane glucose in a sequence combining fermentative biotechnology and synthetic organic chemistry. The first step of the process consists in
fermenting glucose in the presence of a genetically modified Saccharomyces cerevisiae yeast, in which genes coding for different enzymes involved in isoprenoid biosynthetic pathways, in particular β-farnesene have been inserted.17, 18, 19
At this stage,
it is then possible to hydrogenate farnesene to produce hemisqualane - a product currently marketed by the company Amyris under the brand name Hemisqualane. The second step of the biotechnological squalane production process is a chemical synthesis reaction that consists of coupling two farnesene molecules. This complex chemical reaction is carried out in isopropanol - a petroleum solvent - and in the presence
C6 H12 O6 Glucose Figure 4: Fermentation of glucose in isobutene H3 H3 C CH2 C Isobutene CH3 H3 H3
C C
Isododecane Figure 5: Petrochemical derivatives obtained from isobutene
of a palladium-based catalyst. This chemical synthesis leads to squalene and isomers called isosqualenes. In a final third step, squalene is
hydrogenated to squalane, which after purification is of high purity (92% minimum). In this respect, in terms of composition, synthetic squalane is different from olive squalane because it is devoid of cyclic isomers. Instead, it is said to contain linear isomers called iso-squalanes. Therefore, olive and biotech squalanes differ in their isomers, which have been shown to induce different physicochemical and sensory properties.20 Regarding the process inputs, the
production of one ton of biotechnological squalane requires a significant input of sugar and biosynthesis aids: 13.6 tons of glucose, 1 ton of yeast and 1,000 kg of culture medium. A culture medium consisting of a complex
chemical cocktail: ethyl acetate, castor oil heptanol, ethylenediamine tetraacetic acid (EDTA), 3-morpholino-1-propanesulfonic acid (MOPS), citric acid, thiamine hydrochloride, iron citrate, ammonium sulphate, magnesium sulphate and potassium phosphate. These impressive figures show why the biotech squalane plant in Brotas, Brazil, was equipped with a battery of six fermenters with a total capacity of 1.2m litres when it started up. The efficiency of the fermentation process
observed in the laboratory is 35% (Table 1). Finally, the atomic economy of the process as a whole, i.e. from the starting sugar to the finished products, is 28% for hemisqualane and 26% for biotechnological squalane. It should be noted that the latter value is significantly lower than that of olive squalane.
Extraction
Glucose Syrup from Sugaecane
CH2 OH OH OH OH
Squalane ‹‹ Biotech ›› 96%
Figure 6: Production process of biotech squalane PERSONAL CARE April 2022 Hydrogenation
Synthetic Squalene
OH O
Fermentation
GM-Saccharomyces Cerivisiae
Diluted Crude β-Farnesene
from culture media Concentration Purification
β-Farnesene
1. Chemical Coupling6 Pd-Catalyst + Solvent (IPA) T=8°C, t=7h 2.Purification
Having outlined the processes for obtaining
the various bio-based alkanes, what about their environmental impact ? This impact can be measured using the lifecycle assessment (LCA) method.
Environmental impact assessment of bio-based alkanes Environmental impact assessment: the LCA approach LCA is a multi-criteria approach to assessing the environmental and human health impacts of a product or service, taking into account the ‘cradle to grave’ stages. This approach generally covers all stages of the product’s life, from the extraction of raw materials to the disposal of the product. Transport and the use phase are usually included in the analysis. Final disposal may be preceded by recycling and reuse of all or part of the materials involved. LCA methodology is based on a well-established body of normative and academic literature.21, 22, 23
The specific case of cosmetic substances The delimitation of ‘system boundaries’ is an important methodological point for the consistency of the study. In this case, the study carried out is called ‘Cradle to Gate’ and integrates all stages of the product life cycle, from the extraction of raw materials to the exit of the various production sites. The absence of precise data on transport
between suppliers and producers of the four substances studied, as well as the packaging used, makes it impossible to take them into account in this comparative analysis. On the other hand, we can assume that the packaging is quite similar for each of the formulations. When used as ingredients in the
formulation of cosmetic products, the different substances studied can be absorbed by the skin in the case of non-rinsed cosmetic products or discharged into wastewater in the case of rinsed products. The residues that will reach the wastewater after a possible rinsing are difficult to quantify and qualify. Nevertheless, although it is not possible
to speak of recycling of these substances at the end of their life, the material or energy recovery of the co-products throughout the different manufacturing processes of the four formulations is taken into account in the
www.personalcaremagazine.com CH3 CH3 CH3 CH3 H3 C
CH3 C
CH3 CH2
CH3 C
CH3 Polybutene CH3 CH C CH3
GM microorganism Fermentation
C4 H8 + 2 CO2 Isobutene + 2 H2 O
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