Huang S., Schuck P., Jeantet R., Jan G., Chen X.
Soochow University, China

Probiotic efficacy relies on administration of live and active probiotic strains in adequate dose. Growth yield and stress tolerance during probiotic production and delivery thus constitute a key bottleneck. Probiotics are preferably produced, transported, stored and used under a dried form. Spray drying has been long time expected in producing dried probiotics due to its low cost and high productivity. Spray drying of probiotics generally comprises culture, harvesting, washing, re-suspension and drying steps in which preservation of viability remains a quest for the Holy Grail. Therefore, freeze-drying is preferred to spray-drying for producing dried probiotics, as it better preserves the cell viability although it represents subsequently higher production costs (6~10 times higher than spray drying).

Dairy products have been widely used as delivery vehicle of probiotics. We used sweet whey, a dairy industry byproduct, as a two-in-one medium to sustain both growth of probiotics, and direct spray-drying without harvesting, washing and re-suspension steps. Moreover, hyper-concentrated sweet whey was developed to achieve one-step drying with higher production rate.

Both lactic and propionic acid bacteria were adapted to growth within sweet whey. The hyper-concentrated sweet whey produced higher final yield of bacteria population. More remarkably, growth of probiotics in hyper-concentrated sweet whey led to enhanced stress tolerance, overexpression of key stress proteins, accumulation of intracellular storage molecules and compatible solutes, consequently resulting in yet unknown survival upon heat, acid and bile challenges. The cultures were directly spray-dried with various survival rates, depending on sweet whey concentration. Specifically, both lactic and propionic acid bacteria growing in hyper-concentrated sweet whey survived better through spray-drying. The resulting spray-dried powders contained probiotic viability comparable to freeze-drying, reaching to the level of population at 10^10 CFU/g. Furthermore, these powders maintained a considerable stability with constant viability during 4 month storage.

As a conclusion, a new 2-in-1 culture and drying process was developed, using sweet whey as a culture and drying medium. This is to the best of our knowledge the first report describing the feasibility of culturing and direct spray-drying bacteria with hyper-concentrated medium. It triggered multi-tolerance during growth, subsequently leading to the high level of probiotic viabilities remained in the powders after spray drying and following long term storage. Spray-drying being far more cost-effective than freeze-drying, this innovation opens new avenues for sustainable development of probiotic products with enhanced delivery efficiency. This patent-protected new process indeed uses a dairy industry byproduct, requires limited amounts of energy, affords high bacterial viability and protects probiotics from injury undergone within the digestive tract.

Keywords: Probiotics, Delivery vehicle, Stress tolerance, Sweet whey, Spray drying

Huang S., et al. (2016). Major breakthrough in probiotic production: The two-in-one use of sweet  whey affords yet unknown probiotic viability and stability. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 31.). IPC2016

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