Best Practices - Propagating Lactobacillus

Suggestions for propagating Lactobacillus in-house 

1. There's a lengthy section on propagating Lactobacillus in the Milk the Funk Wiki. 
2. In general, Lacto needs simple sugars, complex nitrogen, and pH buffers. 
3. The common "malt extract + apple juice + chalk" approach will work but will not result in optimal cell yields or shelf life. 
4. Use a dedicated vessel for Lactobacillus propagations if you are not able to autoclave (completely sterilize) the propagation vessel and all external parts. It is very common to observe yeast cross-contamination in Lacto props/brinks if the vessel is also used for yeast. 
5. The recommended incubation temperature for most Lactobacillus is between 30-40ºC. 

Quality considerations

We strongly encourage breweries that are propagating microbes in-house to perform quality control analysis on the propagations. For Lactobacillus propagations, we suggest plating onto WLN and MRS agar to check for purity and cross-contamination. Cross-contamination by yeast during Lactobacillus propagations can result in alcohol production, stalled souring, and off flavours. Cross-contamination by other bacteria can result in butyric (vomit), acetic (vinegar), or sulfury (eggy) off-flavours. It is highly recommended to propagate Lactobacillus in a vessel that can be fully autoclaved/sterilized. We recommend a dosing rate of no less than 0.5% inoculum to propagation volume, e.g. 100 mL into 20 L. 

Escarpment Labs is able to work with your brewery on a consultancy basis if you are considering in-house propagation but need some advice from the experts. Contact us for more information.