Antiviral Activity of the Rhamnolipids Mixture from the Antarctic Bacterium Pseudomonas gessardii M15 against Herpes Simplex Viruses and Coronaviruses.

Emerging and re-emerging viruses represent a serious threat to human health at a global level. In particular, enveloped viruses are one of the main causes of viral outbreaks, as recently demonstrated by SARS-CoV-2. An effective strategy to counteract these viruses could be to target the envelope by using surface-active compounds. Rhamnolipids (RLs) are microbial biosurfactants displaying a wide range of bioactivities, such as antibacterial, antifungal and antibiofilm, among others. Being of microbial origin, they are environmentally-friendly, biodegradable, and less toxic than synthetic surfactants. In this work, we explored the antiviral activity of the rhamnolipids mixture (M15RL) produced by the Antarctic bacteria Pseudomonas gessardii M15 against viruses belonging to Coronaviridae and Herpesviridae families. In addition, we investigated the rhamnolipids' mode of action and the possibility of inactivating viruses on treated surfaces. Our results show complete inactivation of HSV-1 and HSV-2 by M15RLs at 6 µg/mL, and of HCoV-229E and SARS-CoV-2 at 25 and 50 µg/mL, respectively. Concerning activity against HCoV-OC43, 80% inhibition of cytopathic effect was recorded, while no activity against naked Poliovirus Type 1 (PV-1) was detectable, suggesting that the antiviral action is mainly directed towards the envelope. In conclusion, we report a significant activity of M15RL against enveloped viruses and demonstrated for the first time the antiviral effect of rhamnolipids against SARS-CoV-2.

Regulatory status quo and prospects for biosurfactants in pharmaceutical applications.

The concept of going 'green' and 'cold' has led to utilizing renewable resources for the synthesis of microbial biosurfactants that are both patient and eco-friendly. In this review, we shed light on the potential and regulatory aspects of biosurfactants in pharmaceutical applications and how they can significantly contribute to novel concepts for the Coronavirus 2019 (COVID-19) vaccine and future treatment. We emphasize that more specific guidelines should be formulated to regulate the approval of biosurfactants for human use. It is also crucial to implement a risk-based approach from the early research and development (R&D) phase in addition to establishing more robust standardized techniques and assays to evaluate the characteristics of biosurfactants.