# Natural Compounds in the Battle against Microorganisms--Linalool
## 5 Conclusions  
Linalool is one of the most important fragrance compounds, as the market for the production of this terpenoid alcohol was estimated to be around USD 10 billion in 2019. It is commonly found in food and used in the production of perfumes, lotions, soaps and shampoos, detergents and cleaning products. An interesting innovation is the possibility of using linalool as an ingredient in active packaging also used in food production. Linalool is mainly obtained by chemical synthesis. However, increasing awareness of climate change, environmental pollution generated by the chemical industry is prompting the search for alternative methods of obtaining this compound. Linalool is a component of many essential oils and can be isolated from them, e.g., by fractional distillation. However, over-harvesting of plants with valuable essential oils can also be associated with negative environmental impacts. Therefore, in order to maintain the sustainability trend in the industry, efficient biotechnological methods for the production of linalool using genetically transformed microorganisms should be sought. Unfortunately, the instability of DNA pathway constructs and the maintenance of a fully functioning metabolic pathway in microorganisms is still a major problem; therefore, the methods developed so far have not gone beyond the laboratory scale. It is worth noting that in fermentation processes, in order to reduce costs, attempts are also being made to use food industry residues or by-products as substrates. Linalool has a number of biological activities as it has antioxidant and anti-inflammatory, antimicrobial, cardioprotective, neuroprotective, sedative, anxiolytic, anticonvulsant and anticancer effects. In terms of its antibacterial activity, it is active mainly against Gram-negative bacteria, as shown in Table 2. It should be remembered that these bacteria, along with Gram-positive bacteria of _Staphylococcus_ spp. and _Enterococcus_ spp., are the main etiological factor of nosocomial infections, i.e., infections that cause a huge problem in medicine all over the world. The main problems that may arise when treating infections caused by Gram-negative bacteria are build-up of resistance to the antibiotics used, the increasing proportion of bacteria with a broad panel of resistance (i.e., non-fermenting rods) in infections, the ability to persist in a hospital environment for long periods andchronic infections. Due to the fact that more and more often in the treatment of these infections, even the so-called last chance antibiotics, linalool seems to be a promising future. Its mechanism of action on microbes is multifaceted, which is important in combating superbugs that mutate at a rapid pace. Therefore, it is worth considering the use of combination therapy--administration of an antibiotic with a natural compound, which is linalool, in the case of synergistic action of both compounds. Such an approach may reduce the emergence of drug resistance to antibiotics of \"last resort\" of microorganisms previously sensitive to them. Therefore, it is puzzling that still little is known about the interactions of linalool with known drugs or with food ingredients. First of all, there are no unequivocal results of research on whether and to what extent linalool acts as an inducer for all CYP isoforms occurring in humans. Therefore, further research is needed in this area using such modern methods as transcriptomics and proteomics techniques, metabolomics, X-ray crystallography, spectroscopy and computer modeling. Clinical trials of the combination of antibiotics with linalool are also necessary, with a particular emphasis on severely ill patients, when factors such as organ failure, increased vascular permeability and renal replacement therapies may alter the pharmacokinetics of any medication used, which may significantly reduce the effectiveness of the treatment undertaken. A somewhat neglected area of research is the biotransformation of linalool.