What happens when wort is left without sufficient saccharomyces during fermentation?

When wort is left without sufficient Saccharomyces during fermentation, it indeed becomes a breeding ground for aggressive microbes. Saccharomyces, particularly Saccharomyces cerevisiae, is the primary yeast strain used in brewing that effectively converts sugars into alcohol and carbon dioxide. If there isn't enough of this yeast present, the fermentation process cannot efficiently proceed.

Without adequate Saccharomyces, the conditions in the wort can become favorable for other microorganisms, such as wild yeasts and bacteria, which may outcompete the desired yeast. This can lead to spoilage, off-flavors, and potentially harmful microbial activity. The presence of these aggressive microbes can not only affect the safety and quality of the beer but also result in fermentation issues, such as the formation of unwanted acids and flavors that deviate from the intended profile of the beer.

Thus, the absence of sufficient yeast creates a situation conducive to contamination and does not allow for the controlled fermentation that is crucial in brewing.