What do microbes release that aids in their growth?

Microbes release digestive enzymes to aid in their growth because these enzymes facilitate the breakdown of complex substances into simpler forms that the microbes can absorb and utilize as nutrients. This process is essential for their metabolism and overall growth. For instance, bacteria in the gut release enzymes that help degrade polysaccharides, proteins, and lipids, allowing them to extract vital nutrients from their environment.

While antibodies are produced by the immune system to combat pathogens, hormones can be chemicals that regulate physiological processes but are not released by microbes for growth. Immune suppressants are substances that can inhibit the immune response, but they are not mechanisms that microbes use to promote their own growth. Thus, digestive enzymes are directly involved in the metabolism of nutrients for microbial growth, making this the correct choice.