Vanillin is a flavoring agent used in food, confection, beverages and pharmaceuticals. Though originally extracted from the vanilla bean, it can be chemically synthesised. However, this results in the formation of byproducts that are environmental pollutants.
This problem can be reduced by using bacteria to transform natural precursors into vanillin. So a team of researchers lead by Shashwati Ghosh Sachan from the Birla Institute of Technology, Ranchi started hunting for bacteria that can transform eugenol into vanillin. Eugenol is a low-cost vanillin precursor found in cloves, nutmeg, cinnamon, basil and bay leaf.
The team isolated sixteen different bacterial colonies from soil samples collected from near the roots of two medicinal plants: Ocimum and Petunia species. Both plants contain eugenol. Near such plants there is a high possibility of finding soil bacteria that can use eugenol.
The researchers screened all the bacterial isolates for strains that could best transform eugenol into vanillin. They used high performance liquid chromatography to assess vanillin production by the strains and selected the strain that showed significant vanillin yield.
Then they characterised the strain at the morphological, biochemical and molecular levels and identified the species as Bacillus safensis.
The team optimised culture conditions for the Bacillus safensis strain. It grew best at 370 degrees centigrade, pH 7, 10% media and agitation at 180 revolutions per minute.
They found that resting cells of the B. safensis strain convert eugenol into vanillin as exclusive metabolite. Using resting cells, they got a stable and efficient vanillin concentration of 120 milligrammes per litre as a single metabolite after 96 hours under optimised conditions.
The strain shows promise for the large scale production of vanillin. Industries using high volumes of vanillin can now protect themselves from the vagaries of the vanillin market.
Biocatal. Biotransformation, 37 (4): 291-303 (2019):
Central University of Kerala
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