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Biofilms find a favorable environment in industrial processes such as food, cosmetic, or medical prosthesis and devices, being responsible of approximately 80% of human bacterial infections. Prevention and/or eradication of microorganism’ films is a worldwide need. There is an increasing interest on the finding and use of novel antimicrobial compounds without side effects. An additional challenge is to fight the antimicrobial resistance that some bacteria and microorganisms develop with traditional antibiotics. Also, in recent years, sustainability and natural source of the antibiofilm chemical principles are also a priority demand. Colloidal systems such as vesicles, particle suspensions, or emulsions are becoming increasingly useful tools for biocompound delivery due to their ability to protect the compound encapsulated against external factors and their possibility to be used as target delivery systems. During the last decade, these types of systems have been widely used for the encapsulation of traditional and novel compounds with antimicrobial properties. The present study summarizes different types of natural compounds tested against several types of bacteria and their feasibility to be encapsulated in different types of colloidal systems.

Rhamnolipid (RL) biosurfactant which is produced by Pseudomonas species is one of the most effective surface-active agents investigated in the literature. Over the years, many efforts have been made and an array of techniques has been developed for the isolation of RL produced strains as well as RL homolog characterization. Reports show that RL productivity by the best-known producer, Pseudomonas aeruginosa, is very diverse, from less than 1 gr/l to more than 200 g L−1. There are some major parameters that can affect RL productivity. These are culture conditions, medium composition, the mode of operation (batch, fed-batch and continuous), bioengineering/gene manipulation and finally extraction methods. The present paper seeks to provide a comprehensive overview on the production of rhamnolipid biosurfactant by different species of Pseudomonas bacteria. In addition, we have extensively reviewed their potential for possible future applications.

An efficient lipopeptide biosurfactant (BS) producer, Aneurinibacillus thermoaerophilus HAK01, was isolated from municipal landfill sites. The strain was able to produce about 4.9 g L−1 lipopeptide at a thermophilic temperature of 45 °C. After optimization of culture component concentrations using the response surface method, the main focus is to find the most appropriate fed-batch strategy to enhance lipopeptide production by the HAK01 strain. For this purpose, four fed-batch strategies including (a) pH-stat mode, (b) constant feeding rate strategy, (c) DO-stat mode, and (d) combined feeding strategy were designed. The production of BS was increased systematically from 4.9 g L−1 in batch mode to 5.9, 7.1, 8.8 and 11.2 g L−1 in each fed-batch mode, respectively. While poor results were obtained in the pH-stat mode, the DO-stat mode showed excellent results in the production of BS. The results of the study confirmed the importance of operational mode, oxygen supply and the kind of feeding strategy in BS production.

Rhamnolipids are one of the most well-known classes of biosurfactants having wide applications in various industries due to low toxicity, high biodegradability, and environmentally friendly. Dissolved oxygen (DO) concentration has the crucial effect on rhamnolipids production, particularly through fed-batch cultivation. In this study, the effect of different levels of DO concentrations on rhamnolipid production by Pseudomonas aeruginosa in both batch and fed-batch fermentation was investigated in a lab-scale fermenter under precise DO control. A maximal rhamnolipid production of 22.5 g/l was obtained at a DO concentration of 40% in batch fermentation. In order to achieve the high rhamnolipid production, a fed-batch operation under tight DO control of 40% was conducted. As a result, the overall rhamnolipid production and productivity reached to 240 g/l and 0.9 (g/l h), corresponding to a 10.7 and 4.8-fold improvement compared to the batch experiments. The high level of rhamnolipid production via the fed-batch cultivation can be attributed to both DO concentration and the feeding strategy. This achievement is promising for the production of rhamnolipid in industrial scale.

Rhamnolipid (RL) biosurfactant which is produced by

An efficient lipopeptide biosurfactant (BS) producer