The so-called high gravity brewing, i.e. brewing at elevated original gravities of 15 °P and higher, poses an alternative to traditional brewing. This approach aims for “concentrated beers” which can be diluted just before bottle-filling and thus achieving higher efficiency due to lower need for water, electricity, manpower or logistics. The yeast, however, is stressed more compared to traditional brewing, facing higher osmotic pressure at the start of the fermentation as well as higher ethanol pressure in the end. As a result, the fermentation can get stuck or the usual repitching of the yeast for the next brew cannot be done due to the alteration of the yeast. Consequently, there is a limit of original gravity to be used for high gravity brewing which impedes further economic progress.
The VLB Berlin started a research project (supported by the Federal Ministry of Economic Affairs and Energy; INNOKOM VF; 49VF180009) to overcome those limitations and get further economic value out of high gravity brewing. Within this research project, a fed-batch fermentation process is to be established: the fermentation starts at a usual original gravity and will then be fed by highly concentrated wort in order to avoid the high osmotic pressure in the beginning. The process development will be done in the miniaturized fermentation platform BioLector Pro allowing for conducting experiments in batch as well as fed-batch mode at µL-scale and thus reaching high throughput and providing online measurement data of e.g. biomass pH or pO2.
These online-data are then used to set up a mechanistic model describing the process of consecutively fermenting the different wort sugars and producing ethanol. The model will be used for further process development resulting in adequate feeding strategies achieving highly efficient conversion of sugars into ethanol.
The final aim is a fed-batch strategy for high gravity brewing that is supported by a mechanistic model which can universally be used for different brewer’s yeasts and that can be transferred to industrial scale as well.