ARTICLE FEED & ADDITIVE MAGAZINE July 2024 75 production, all fermentation steps are carried out under aerobic conditions in order to ensure optimal biomass growth. Multiplication is scaled-up stepwise: from a few milliliters of a pure culture of the desired strain (kept at -80°C), to an industrial fermenter that can reach a few hundred m3 (steps 1-4). The main challenges of yeast production are to ensure proper yields and outputs (live biomass) and optimal performance (metabolic activity) of the end-product for users, while preventing the presence of contaminating microbes. These objectives can be accomplished thanks to meticulously controlled conditions and tight quality control along the process. In particular, all physico-chemical parameters such as medium composition, temperature, pH, nutrients concentration and agitation are strictly controlled during the whole process. These parameters are determinant for the product’s final activity and efficacy, and each yeast strain has its own optimal conditions. Hence, for each strain these conditions have been carefully determined at lab and pilot scales before industrialization. The parameters are thoroughly controlled from seed to final formulation to ensure consistency of the final product. HARVEST AND FURTHER PROCESSING At the end of the fermentation (propagation) step (4), the resulting biomass of cells is harvested. This is done by centrifugation (5) to separate the cells from the media. Cells can be washed to remove any remaining media and finally collected as a yeast cream (18 – 20 % dry weight). The yeast cream is stored at < 5°C until further processing. From there, the process differs according to the desired yeast product (live yeast or yeast derivatives). When producing live yeast, the yeast cream is sent to a rotary vacuum filter to remove further moisture QC TESTS LALLEMAND YEAST CULTURE COLLECTION FEED STORAGE TRANSPORTATION PACKAGING DRYING EXTRUSION FILTRATION INOCULUM PREPARATION SEED FERMENTATION INDUSTRIAL FERMENTATION HARVEST OF THE BIOMASS YEAST CREAM STORAGE QC TESTS • Strain identity • Microbial purity • Viability CUSTOMER ANALYSIS • Viability and stability Studies in final customers application (feed, pellets...) FINISHED PRODUCT ANALYSIS • Microbial purity • Viability • Dry substance • Stability studies • Particle size • Color CERTIFICATE OF ANALYSIS RELEASED FOR EVERY BATCH OF LIVE YEAST • Microbial purity • Biomass growth QC TESTS • Microbial purity • Biomass growth • Viability QC TESTS • Microbial purity • Biomass growth • Viability • Protein content • Trehalose content Figure 1. Live yeast production process and QC tests.
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