THE ROLES OF MAGNESIUM IN BIOTECHNOLOGY

This review highlights the important roles played by magnesium in the growth and metabolic functions of microbial and animal cells, and ther efore assigns a key role for magnesium ions in biotechnology. The fund amental biochemical and physiological actions of magnesium as a regula tory cation are outlined. Such actions are deemed to be relevant in an applied sense, because Mg2+ availability in cell culture and fermenta tion media can dramatically influence growth and metabolism of cells. Manipulation of extracellular and intracellular magnesium ions can thu s be envisaged as a relatively simplistic, but nevertheless versatile, means of physiological cell engineering. In addition, biological anta gonism between calcium and magnesium at the molecular level may have p rofound consequences for the optimization of biotechnological processe s that exploit cells. In fermentation, for example, it is argued that the efficiency of microbial conversion of substrate to product may be improved by altering Mg:Ca concentration ratios in industrial feedstoc ks in a way that makes more magnesium available to the cells. With par ticular respect to yeast-based biotechnologies, magnesium availability is seen as being crucially important in governing central pathways of carbohydrate catabolism, especially ethanolic fermentation. It is pro posed that such influences of magnesium ions are expressed at the comb ined levels of key enzyme activation and cell membrane stabilization. The former ensures optimum now of substrate to ethanol and the latter acts to protect yeasts from physical and chemical stress.