At Senyo, developing ferrous-enriched yeast combines strain selection, strain improvement, cultivation and downstream processing. This R&D note outlines the steps used in our development work and the considerations that guide them.
Selecting the starting strain
We screen yeast strains held in the laboratory using two main criteria: biomass production and the ability to accumulate iron. Initial screening is followed by further selection to compare strain performance.
Yeast growth and iron enrichment need to be considered together. A strain that produces more biomass does not necessarily accumulate more iron, so selection considers the balance between these characteristics.
Improving strains through mutation and adaptation
Our strain-development work uses mutation and adaptation to improve iron tolerance and enrichment performance. Methods used in this process include:
- UV mutagenesis: exposing yeast cultures to ultraviolet light and selecting strains under elevated iron conditions.
- Chemical mutagenesis: using chemical mutagens, including diethyl sulfate (DES), in strain-development work.
- Microwave mutagenesis: treating yeast cultures with microwave irradiation, followed by repeated screening and serial culture to assess strain stability.
- Hybrid breeding: combining useful characteristics from different parent strains.
From cultivation to processing
The process proceeds through the following stages:
- Slant culture: activating and purifying the starting yeast culture.
- Primary liquid seed culture: expanding the culture.
- Secondary liquid seed culture: carrying out a further stage of culture expansion.
- Fermenter cultivation: growing the yeast in an iron-containing medium for enrichment.
- Separation and washing: collecting the yeast cells and removing residual inorganic ions.
- High-temperature treatment: carrying out the heat-treatment stage of the process.
- Spray drying: converting the material into a dry powder.
- Milling and packaging: completing powder processing, finished-product inspection and packaging.
These stages connect strain-development work with the cultivation and processing of ferrous-enriched yeast.