Role of magnesium ions on yeast performance during very high gravity fermentation

Abstract

The advent of highly efficient, environmentally friendly and cost effective fermentation technology has given impetus to research in the field of optimizing nutritional parameters for optimum yeast fermentative performance. Very high gravity fermentation is a novel fermentation technology that provides an increased production capacity from same size fermentation facilities, with outstanding benefits that includes: high ethanol yield per fermentable mash, considerable savings in energy and process water usage, and effluents with low biological oxygen demand amongst others. Limitations to full commercialization of the technology have been attributed to deleterious effects of the fermentation condition on yeast physiology which include high osmotic stress and ethanol toxicity amongst others. The impact of these physiological stresses on yeast cells during high substrate fermentation manifest as sluggish and incomplete fermentation with high residual sugars in beer, reduced ethanol yield, disproportionate synthesis of esters and generation of respiratory deficient yeast crop. However, compelling evidence has implicated magnesium ions with numerous biological processes and more importantly, with the role of curtailing the impact of these stress conditions. Hence, this review highlights two potential stress conditions of very high gravity fermentation; their mechanism of inhibition versus yeast stress response mechanism, role of magnesium ions in yeast physiology and its impact on fermentation processes. The knowledge emphasized herein will be of practical importance to industrial fermentation processes, as it provides feasible clues to improving yeast fermentative performance under high substrate conditions -with perspectives to precise magnesium regulation in yeast.

Comparison of four extraction methods for analysis of volatile hop-derived aroma compounds in beer

“…The chemistry of hop‐derived compounds in beer is very complex; comprised many compounds from different chemical groups, including alcohols, esters, aldehydes, ketones, acids, terpenoids, phenols, and sulfur compounds . Differences in VOC composition in beer arise from specific hop cultivars, malt types, yeast strains used, and the interactions that occur between these three components, which in part are also influenced by characteristics of the water . The VOCs in beer contribute significantly to its style, flavor, quality and consumer preference.…”

Microencapsulation of Baker’s Yeast in Gellan Gum Beads Used in Repeated Cycles of Glucose Fermentation

“…The calcium ion can adhere to the negatively charged cell plasma membrane and thus increase its stability to stressors that may occur in the fermentative processes [41,53]. In this manner, yeast cells could assist in the reinforcement of the network and as a consequence increase its mechanical stability.…”

“…The calcium ions, in high concentrations, can replace the magnesium in a number of biochemical processes which can lead to cell growth and to maintaining the cell viability. Also, increasing the calcium concentration in the fermentation medium has a buffer effect which prevents the increase of pH in the environment and leads to an increased fermentation efficiency [41,42]. The originality of this study is primarily related to the pregelification of the gellan solution, before the capillary extrusion, using low concentrations of CaCl 2 which leads to a viscosity increase of the polysaccharide solution.…”

Screening of yeast isolates from flowers for effective ethanol production

“…It counteracts the toxic effects of Cu, Co, Cd, and Al. Magnesium has been reported to regulate metabolic enzymes of the fermentative pathway (via pyruvate decarboxylase) or the respiratory pathway (via pyruvate dehydrogenase) and the switching between respiratory and fermentative processes (Rees and Stewart, 1997;Walker, 2004;Walker et al, 2006;Udeh and Kgatla, 2013). Meanwhile, calcium is involved in regulating amylase activity and phosphate precipitation and also plays a protective role for cell membranes (Walker, 2004;Trofimova et al, 2010).…”