@article {Osburn121103, author = {Kara Osburn and Justin Amaral and Sara R. Metcalf and David M. Nickens and Cody M. Rogers and Christopher Sausen and Robert Caputo and Justin Miller and Hongde Li and Jason M. Tennessen and Matthew L. Bochman}, title = {Primary souring: a novel bacteria-free method for sour beer production}, elocation-id = {121103}, year = {2017}, doi = {10.1101/121103}, publisher = {Cold Spring Harbor Laboratory}, abstract = {In the beverage fermentation industry, especially at the craft or micro level, there is a movement to incorporate as many local ingredients as possible to both capture terroir and stimulate local economies. In the case of craft beer, this has traditionally only encompassed locally sourced barley, hops, and other agricultural adjuncts. The identification and use of novel yeasts in brewing lags behind. We sought to bridge this gap by bio-prospecting for wild yeasts, with a focus on the American Midwest. We isolated 284 different strains from 54 species of yeast and have begun to determine their fermentation characteristics. During this work, we found several isolates of five species that produce lactic acid and ethanol during wort fermentation: Hanseniaspora vineae, Lachancea fermentati, Lachancea thermotolerans, Schizosaccharomyces japonicus, and Wickerhamomyces anomalus. Tested representatives of these species yielded excellent attenuation, lactic acid production, and sensory characteristics, positioning them as viable alternatives to lactic acid bacteria (LAB) for the production of sour beers. Indeed, we suggest a new LAB-free paradigm for sour beer production that we term {\textquotedblleft}primary souring{\textquotedblright} because the lactic acid production and resultant pH decrease occurs during primary fermentation, as opposed to kettle souring or souring via mixed culture fermentation.Chemical compounds studied in this article Lactic acid (PubChem CID: 612); Ethanol (PubChem CID: 702)AbbreviationsABValcohol by volumeDICdifferential interference contrastEtOHethanolFGfinal gravitygDNAgenomic DNAIBUinternational bittering unitLABlactic acid bacteriaLASSOlactic acid specific soft-agar overlayN-Jneighbor-joiningOGoriginal gravityWLNWallerstein Laboratories nutrientYPDyeast extract, peptone, and dextroseAbbreviationsABValcohol by volumeDICdifferential interference contrastEtOHethanolFGfinal gravitygDNAgenomic DNAIBUinternational bittering unitLABlactic acid bacteriaLASSOlactic acid specific soft-agar overlayN-Jneighbor-joiningOGoriginal gravityWLNWallerstein Laboratories nutrientYPDyeast extract, peptone, and dextrose}, URL = {https://www.biorxiv.org/content/early/2017/03/27/121103}, eprint = {https://www.biorxiv.org/content/early/2017/03/27/121103.full.pdf}, journal = {bioRxiv} }