January 12/Journal of Technology & Science -- "To date, only recombinant chymosin has been obtained in its active form from supernatants of filamentous fungi, which are not as good candidates as yeasts for large-scale fermentations. Since Bos taurus chymosin was cloned and expressed, the world demand for this protease has increased to such an extent that the cheesemaking industry has been looking for novel sources of chymosin," investigators in Spain report.

"In this sense, because buffalo chymosin has properties that are more stable than those of B. taurus chymosin, it may occupy a space of its own in the chymosin market. The main objective of the present work was the production of active recombinant buffalo chymosin in the culture supernatant of Pichia pastoris. This yeast has demonstrated its usefulness as an excellent large-scale fermentation tool for the secretion of recombinant foreign proteins. RNA was extracted from the abomasum of a suckling calf water buffalo (Bubalus arnee bubalis). Preprochymosin, prochymosin, and chymosin DNA sequences were isolated and expressed into P. pastoris. Only the recombinant clones of P. pastoris containing the prochymosin sequence gene were able to secrete the active form of the chymosin to the culture supernatant. This paper describes for the first time the production of active recombinant chymosin in P. pastoris without the need of a previous in vitro activation," wrote J.A. Vallejo and colleagues, University of Santiago.

The researchers concluded, "The new recombinant yeast strain could represent a novel and excellent source of rennet for the cheesemaking industry."

Vallejo and colleagues published their study in the Journal of Agricultural and Food Chemistry ("Cloning and Expression of Buffalo Active Chymosin in Pichia pastoris." Journal of Agricultural and Food Chemistry, 2008;56(22):10606-10610).

For additional information, contact T.G. Villa, University of Santiago, Faculty Pharmacy, Dept. of Microbiology, Santiago De Compostela 15782, Spain.

The publisher of the Journal of Agricultural and Food Chemistry can be contacted at: American Chemical Society, 1155 16th St., NW, Washington, DC 20036, USA.

From the January 19, 2009, Prepared Foods E-dition