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Less-studied yeast species, Pichia guilliermondii, examined as juvenile rainbow trout additive

May 20, 2022  By Ruby Gonzalez


Mortality of rainbow trout fed Pichia guilliermondii (CitriStim® labeled as C) and and/or a commercial dietary gut supplement (Anco® FIT labeled as A). (Photo: Journal of World Aquaculture Society)

The potential of Pichia guilliermondii as functional additives in juvenile rainbow trout is good news for consumers.

“The identification of a variety of vifuncitable yeast products in rainbow trout could induce more price competition and potentially reduce costs associated with including these products in commercial feeds,” Dr. Wendy Sealey, told Hatchery International.

Sealey is the corresponding author of “Evaluation of the ability of Pichia guilliermondii to improve growth performance and disease resistance in rainbow trout (Oncorhynchus mykiss).” She is with the USDA, Agricultural Research Service, Bozeman Fish Technology Center in Montana.

Sealey adds that this would provide feed manufacturers and trout producers the flexibility of increased utilization of the products to improve trout production efficiency.

The trials ended with supplementation of either P. guilliermondii or the gut supplement improving growth and food conversion efficiency in juvenile rainbow trout when fed for 16-weeks in a recirculating aquaculture system (RAS).
“Pichia guilliermondii and gut supplement both increased feed intake and protein retention efficiency in rainbow trout leading to improved feed conversion ratio and growth and suggesting improved gut health in the supplemented animals,” she explained.

P. guilliermondii results as a spent yeast by-product following the microbial fermentation of carbohydrates by the yeast in the commercial production of citric acid.

“There is a need for research examining the efficacy of novel and less-studied, non-saccharomyces yeast species, including Pichia guilliermondii that can be by-products of these and other biotechnological applications,” she said.

A lot of that has looked into yeast and yeast-derived products as additives in fish have focused on Saccharomyces cerevisiae. Readily available, it is a by-product generated from many industrial processes, including beer, alcohol and bio-ethanol production.

The research, published on the Journal of World Aquaculture Society, showed that animals fed with an extruded diet supplemented with 0.3 or 0.6 per cent P. guilliermondii alone or 0.3 per cent P. guilliermondii with a dietary gut supplement at 0.1 per cent improved growth and food conversion efficiency in rainbow trout when fed for 16-weeks. No effect of supplementation on mortality was observed.

Commercially available products were used in the fish diets. P. guilliermondii was supplied through, CitriStim. Anco FIT was used as gut supplement containing active natural ingredients

Ease of delivery and cost-effectiveness, she said, are strong points of using products derived from yeast culture. These have been used as additives in human and terrestrial animal feed ingredients long before finding their way in fish diet.


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