###### Abstract  
Amazake is a traditional, sweet, non-alcoholic Japanese beverage typically produced through koji fermentation by the fungus _Aspergillus oryzae_. However, alternative microorganisms such as _Bacillus amyloidiquefaciens_ offer potential advantages and novel possibilities for producing similar fermented beverages. This study aimed to replicate the ancestral beverage of amazake by replacing _A. oryzae_ (W-20) with _B. amyloidiquefaciens_ (NCIMB 12077) and comparing their fermentation processes and resulting products. Our results show that the production of amazake with _B. amyloidiquefaciens_ (ABA) is not only possible but also results in a beverage that is otherwise distinct from traditional amazake (AAO). Saccharification was achievable in ABA at higher temperatures than in AAO, albeit with lower reducing sugar and enzymatic activity values. Amino acids and organic acids were more abundant in AAO, with cysteine being uniquely present in AAO and shikimic acid only being present in ABA. The volatile aroma compound profiles differed between the two beverages, with AAO exhibiting a greater abundance of aldehydes, and ABA a greater abundance of ketones and alcohols. Interestingly, despite these compositional differences, the two beverages showed similar consumer panel acceptance rates. An analysis of their microbial communities revealed pronounced differences between the amazakes, as well as temporal changes in ABA but not in AAO. This study provides promising insights into harnessing the potential of _B. amyloidiquefaciens_ as the primary microorganism in the fermentation process of amazake-like beverages, marking an important advancement in the field of fermented low-alcohol beverage production, with possible applications in other fermented foods. amazake; fermentation; _Aspergillus oryzae_; _Bacillus amyloidiquefaciens_; enzymatic activity; reducing sugars; metabolomics; metagenomics; sensory analysis 2020  
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Amazake, a traditional Japanese sweet, non-alcoholic drink, has been consumed for over a thousand years [2]. It is produced by adding water and steamed rice to rice koji and incubating at 55-60 \({}^{\circ}\)C in an anaerobic environment for several hours [3]. The primary process in amazake production is saccharification, in which rice starches are transformed into simple sugars by enzymes released during the koji fermentation [4]. Amazake's rising popularity in recent years can be attributed in part to its reported health benefits, such as its antifatigue effect and skin barrier functions, among others [5; 6; 7]. Despite its long history and popularity, many aspects of traditional amazake production remain unknown. For example, the microbial diversity and protease activity are unexplored, and the amylase activity has only been reported on during the early stages of the fermentation process [4]. This study aims to investigate the dynamics of the fermentation at a deeper level. _A. oryzae_ and other molds are highly valued for their ability to secrete enzymes and are, thus, often considered the default option for processes where exogenous enzymatic effects are desired. In contrast, although bacteria are common in many kinds of food fermentations, they are often underutilized for their ability to secrete enzymes [8]. However, bacterial enzymes can be produced under a wide range of conditions. By exploring alternative microorganisms adaptable to diverse environments, we aim to expand the range of microbial candidates for fermentation processes [9; 10]. Through investigating such alternatives [9], there is potential not only to improve the efficiency and scalability but also to enhance the gastrointestinal and nutritional benefits in amazake manufacturing. One such microorganism is _Bacillus amyloliquefaciens_, an endospore-forming bacterium commonly found in soil, water, and various food products [11]. Apart from its antifungal function, _B.