Alcohol School speakers discuss yeast physiology, nutrition

By Lisa Gibson | September 10, 2019

During the morning session Sept. 10 of the Alcohol School in Montreal, Graeme Walker, scientific director of the Ethanol Technology Institute in Scotland, discussed yeast behaviors and physiology, but also listed ways to increase yield by 3 percent. “Is that helpful? In the fuel industry, yes,” Walker said. He listed a few ways including: minimize microbial contaminants; optimize yeast nutrition; minimize yeast stress and remove inhibitors; precondition yeast and use nonflocculent strains; reduce glycerol and other secondary yeast metabolites; and use the correct bioprocess.

The strain of yeast is very important, but think of environment and media, also, he told his audience. Yeast is important, but is perhaps the least understood of the elements in the alcohol-production process.

He addressed factors that affect growth and fermentation, including genotype, nutrient availability and environmental factors such as temperature, pH, agitation, sheer and pressure.

Following Walker, Jim Miers, nutrient category manager of Lallemand Biofuels & Distilled Spirits, discussed yeast nutrition. He started by telling the audience it’s in their best interest to take vitamin supplements. Yeast behaves much like human cells, taking in its food source, digesting, growing and eventually dying, Miers said.

“The main goal here is to keep the growth rate as high as possible in anaerobic conditions,” he added.

Miers echoed Walker when he said good fermentation requires proper environment, conditions, minimized infection and minimized stress inside the fermentor. “The yeast cell, to me, is amazing,” he said, adding that conditions change constantly in the fermentor and yeast adapts. For consistent, successful fermentation, it’s crucial to understand the composition of the material, as well as the nutrient and environmental requirements of yeast.

Major nutrients for yeast include usable nitrogen, oxygen, phosphorus, sulfur and carbohydrates, Miers said. Macroelements include calcium, iron, manganese, chloride, magnesium and zinc. Microelements needed are cobalt, boron, cadmium, iodine, molybdenum, nickel and vanadium.

“Good nutrition = good fermentation!” stretched across the bottom of Miers’ final presentati