The notion of using brazzein – a protein from the fruit of the West African climbing plant pentadiplandra brazzeana baillon (Oubli) – as a potential sugar substitute is by no means new.
But making it in large amounts, however, has been challenging. It has been argued that purifying it from the fruit on a commercial scale is difficult.
“[Brazzein] has attracted much attention as a candidate sweetener because of its high sweetness intensity, sugar-like taste, and good stability at high temperature, and wide range of pH values,” notes the article, published in the Journal of Agricultural and Food Chemistry.
Now new research led by Kwang-Hoon Kong from Korea’s Chung-Ang University and in association with Augusta University, highlights a new approach using yeast to churn out brazzein.
Working with kluyveromyces lactis, the researchers used the yeast to overproduce two proteins that are essential for assembling brazzein.
By doing so, the team made 2.6 times more brazzein than they had before with the same organism.
A panel of tasters found that the protein produced by this approach was more than 2,000 times sweeter than sugar.
“Potential mass production could provide a valuable opportunity for the commercial use of brazzein,” states the study. “Brazzein secretion levels in the yeast expression system could be elevated by optimizing the expression conditions, the gene copy number, overexpressing molecular chaperones, foldases, genes associated with the secretory pathway, and so on,” the paper adds.
Extraction limitations
In recent years researchers have made several attempts produce to brazzein in microorganisms and transgenic plants because of the difficulty and limitations in obtaining the natural source.
For example, previous studies of brazzein expression in escherichia coli reported that the recombinant brazzein was insoluble and required several purification steps, resulting in a low overall yield.
Meanwhile brazzein production in transgenic maize resulted in low purification yields and cross-contamination.
There was more success when using the yeast pichia pastoris, with the purified brazzein obtained in a soluble and active form at approximately 30−90 mg/L.9
However, it is believed kluyveromyces lactis offers greater potential.
“The recombinant brazzein expressed was purified by CM-Sepharose column chromatography, and approximately 104 mg/L was obtained. This yeast expression system is regarded as suitable for commercialisation of brazzein in the food industry because of its food grade status and excellent fermentation characteristics on a large scale,” the article concludes.
Source: Journal of Agricultural and Food Chemistry
July 2016. DOI: 10.1021/acs.jafc.6b02446
“Improved Secretory Production of the Sweet-Tasting Protein, Brazzein, in Kluyveromyces lactis.”
Authors: Kwang-Hoon Kong, et al