# The Viable but Non-Culturable (VBNC) State, a Poorly Explored Aspect of Beneficial Bacteria
## 3 The VBNC State in Beneficial Bacteria
### Firmicutes and the VBNC State  
_Bacillus coagul_s is a species of Firmicutes that is considered probiotic-safe. This bacterium has the ability to endure high temperatures and it has developed genetic stability through several years of commercial production [95]. Its main benefits for human health include the modulation of gastrointestinal disorders, immune system stimulation, and lowering cholesterol [96]. This bacterium can form endospores and survive for decades in unfavorable environmental conditions. It was previously thought that its high persistence was due only to its ability to form spores; however, it has been observed that _B. coagul_s can enter the VBNC state as a strategy to face adverse conditions [57]. Little is known about the return to cultivability when humans consume these beneficial microorganisms. Some studies have shown that bacteria secrete certain specific proteins to exit the latency state [97], which is a possibility in the case of _B. coagul_s. This represents a task for future research. If we consider that some beneficial bacteria are capable of returning to the culturable state when they interact with their hosts [4], it is very likely that, although culturable bacteria are not detected in fermented foods, when they are consumed by humans, the conditions present in these hosts may favor their return to a cultivable state, being able to exercise their beneficial properties. _Lactiplantibacillus plantarum_ is a Firmicutes species widely distributed in various environments, such as the gastrointestinal, vaginal, and urogenital tracts, and in dairy products, vegetables, meat, hay, and wine. This ability to adapt to different conditions demonstrates its metabolic diversity [98], having potential for various applications. The main applications of _L. plantarum_ include the fermentation of foods such as cheese, kefir, sauerkraut, fermented meat products, fermented vegetables, and beverages [99]. It has been reportedthat _L. plantarum_ produces antimicrobial substances such as plantaricin [100] and can remove microcystins, the main toxins produced by cyanobacteria [101], which makes it an alternative food preservative or a compound to fight infections. Studies of the VBNC state in _L. plantarum_ have reported that it can remain latent during beer storage, which contributes to the deterioration of this beverage [20]. Another study showed that _L. plantarum_ in the VBNC state can inhibit microcystins, which contributes to the preservation of fermented foods [101]. It is interesting to observe that the VBNC state in this species can be detrimental for beer production but beneficial for food preservation, reflecting the versatility of non-culturable _L. plantarum_ to continue performing its functions. This suggests that when used as a probiotic to improve human health, it can provide its benefits without being culturable. In short, it is a microorganism that should be studied in greater depth, particularly regarding what happens during the VBNC state, to take advantage of its diversity of applications. In the production of alcoholic beverages, the involvement of microorganisms is crucial for successful fermentation. A significant challenge in the brewing and winemaking industry is the spoilage of wine and beer by lactic acid bacteria, which have the ability to enter the VBNC state [20]. _Oenococcus oeni_ is a Firmicutes bacterium, belonging to the lactic acid bacteria group, adapted to the stressful environment of wine. It is widely used as a starter microorganism to carry out malolactic fermentation (MLF), where L-malate is converted into L-lactate [102]. The use of starter cultures of _O. oeni_ remains difficult in some wine regions, due to the hostile environment created by the low pH and the presence of SO\({}_{2}\) and ethanol [103]. The ability of _O. oeni_ to respond these stress conditions has great relevance in terms of increasing wine production at a lower cost. Thus far, knowledge of the VBNC status of _O. oeni_ is limited.