"The results presented are the first steps toward the design of more efficient, continuous or semicontinuous processes, suggesting a potential alternative to produce beta-cryptoxanthin for commercial production," wrote the authors in the Journal of Food Science (Vol. 71, pp. E314-E319).
Beta-cryptoxanthin, found naturally in many citrus fruits, mangos and papaya, is a provitamin A carotenoid, meaning it is converted to vitamin A in the body. A growing number of studies have linked increased intake of the carotenoid to a lower risk of many diseases such as heart disease, skin cancer, prostate cancer, and arthritis.
The new production method uses fermentation technology with the Flavobacterium lutescens ITCB008, a bacterial strain that has been extensively studies for production of the non-provitamin A carotenoid zeaxanthin, and beta-cryptoxanthin is known to be an intermediate in the production of this carotenoid.
The researchers, from the Department of Chemical and Biochemical Engineering at the Technological Institute of Celaya, added small concentrations of sodium chloride, magnesium sulphate, and potassium phosphate, because such alkaloid salts have been proposed to inhibit the steps that convert the cryptoxanthin to zeaxanthin, and lead to the accumulation of beta-cryptoxanthin in the cytoplasm of the cells.
"Seemingly, the inorganic salts used has an unexpectedly strong positive effect of beta-cryptoxanthin production at the expense of zeaxanthin formation," wrote the scientists.
"In addition, the changes of magnesium and potassium concentration seem to suggest that it acts as enzyme cofactor in the biosynthesis of beta-cryptoxanthin."
The whole fermentation process was optimised in terms of agitation, aeration, temperature and acidity, and the researchers reported that the following values produced the highest yield - agitation: 190 rpm, aeration: 0.086 VVM, temperature: 27.6 Celsius, pH: 7.3.
An extraction method using ethanol was used, since this solvent is suitable to products intended for human consumption, and 770 milligrams of beta- cryptoxanthin per kilogram of mass cell (dry weight) was recovered after 28 hours.
"We can note that this concentration surpasses the values reported for natural sources, and other similar processes for carotenoids production," wrote the researchers.
High pressure liquid chromatography analysis of the extracted carotenoids showed that beta-cryptoxanthin was the main carotenoid produced, accounting for 95 per cent of all the total carotenoid content.
"Clearly the process described in this study has significant advantages: first, higher yield than those reported by similar processes for carotenoids production, as well as contents reported for natural sources; second, a simple down-stream processing with high product recovery," concluded the scientists.