Mannoproteins from inactivated whole cells of baker's and brewer's yeasts as functional food ingredients: Isolation and optimization.

Abstract

Because of the structural multiplicity of yeast mannoproteins, they have shown a great interest as food ingredients for a wide range of applications. The yields and the structural properties of mannoproteins varied depending on the isolation methods and their sources (baker's and brewer's Saccharomyces cerevisiae yeasts). Noncovalently bound mannoproteins (6.5kDa) with a mannan/protein ratio of 0.63 and 2.78 were recovered upon the heat treatment of brewer's and baker's yeasts, respectively, whereas sodium dodecyl sulfate treatment led mainly to the release of nonglycosylated proteins. The highest yield of mannoproteins was achieved upon the enzymatic isolation with Zymolyase® from Arthrobacter luteus. The recovered covalently bound mannoproteins were characterized by a higher mannan/protein ratio (13.1 to 42.7) and a wider molecular weight distribution (5 to 10kDa; 10 to 100kDa; 100 to 400kDa). Predictive models were developed to understand and modulate the effects of isolation parameters on yield, the mannoproteins content, and the mannan/protein ratio. The enzyme concentration was the most significant parameter affecting the yield, whereas the reaction time was the most significant parameter affecting mannan/protein ratio. Comparison of predicted and experimental values validated the established predicted models for the isolation of well-defined mannoproteins from yeast for targeted food applications. PRACTICAL APPLICATION: The increasing demand for clean label health-promoting foods has fueled the development of highly functional ingredients that offer both techno-functionalities and health-promoting properties. This study reveals the efficiency of whole inactivated yeasts as sources of mannoproteins. Given the dependence of the techno-functional and health-promoting properties of mannoproteins on their molecular properties, the investigation of the effects of the yeast sources and the type of isolation methods on the structural properties of mannoproteins would allow the modulation of their properties. Furthermore, the developed predictive models for the enzymatic process are expected to enhance the isolation efficiency of mannoproteins with well-defined structures.