# Evaluation of Non-_Saccharomyces_ Yeast for Low-Alcohol Beer Production
## 1 Introduction  
In recent years, there has been a multidirectional growth of a brewing industry. One such direction is the so-called craft beer revolution. It is safe to say that nowadays, brewers and consumers are reading the benefits of this movement. Prior to 2009, craft beer sales accounted for less than 2% globally, which nearly doubled to 3.9% in 2021 [1, 2]. Thanks to that, consumers are continually looking for new, unique products. According to [PERSON] [2], the relatively new market of reduced/no alcohol beers can be seen as an extension of the craft beer revolution. Although these beers have a relatively low market share, it is constantly growing [3]. According to [PERSON] et al. [4], non-alcoholic beer (containing up to 0.5% ethanol) accounted for 3.8% of European beer volume in 2019. [PERSON] [2] states that no-lo beers already have 3% of the global market, with further growths expected. With such a potential, the brewing industry is looking for new ways to produce these beers. Producing a beer with a normal alcohol content and then removing that alcohol to obtain desired levels is not energetically viable and problematic in many regards. An interesting alternative to these methods is to produce a beer with reduced alcohol levels in the first place using biological methods. Among the methods which enable this, using non-_Saccharomyces_ yeast has gained a great interest [5]. For a long time, _Saccharomyces cerevisiae_ was the main yeast species used in most of fermentative industries. This is related to their unique biological characteristics of high fermentation capacity, good alcohol production, and elevated resistance to adverseenvironmental conditions [6]. The other yeast species found in fermentation environments, non-_Saccharomyces_ yeast, were thought to be a source of microbiological spoilage rather than a desired organism. However, in recent decades this view has begun to shift. For example, they are now seen as a factor which can add a complexity to the flavor profile of wines [7]. The brewing science has also expressed interest in these yeasts, as their application can result in beers with unique sensory characteristics. This is related to the high bioflavoring potential of some of the strains. Individual strains can be characterized by desirable profiles of volatile compounds [8; 9; 10]. As an extension of bioflavoring potential, some strains possess higher enzymatic activities of \(\beta\)-glucosidase and \(\beta\)-lyase than _S. cerevisiae_[11]. These enzymatic activities can result in a beer with more pronounced fruity, citrus, or tropical aromas, due to the release of flavor compounds from their precursors [12]. However, the main problem with non-_Saccharomyces_ yeasts is the fact that the majority of them are poor fermenters, which makes them problematic to use in standard beer fermentations. This has been evident in wine studies and is even more problematic in the case of the brewing industry. The fermentative sugars found in brewers wort are glucose (10-15%), fructose (1-2%), sucrose (1-2%), maltose (50-60%), and maltotriose (15-20%) [13]. _S. cerevisiae_ yeast are characterized by a high fermentative capacity, as they readily utilize sugars found in wort (except for the maltotriose, which utilization is strain-dependent). As maltose is the major sugar found in the brewers' wort, using yeasts which are unable to ferment this sugar would result in a beer with a reduced alcohol content. The ability to utilize maltose is rather scarce among non-_Saccharomyces_ yeasts. However, this potential drawback can also be seen as their biggest advantage regarding the production of reducedalcohol beer. This approach would be easy to implement in most breweries as the only factor that would change about the production process is the applied yeast species [3; 14; 15; 16].