Foaming of rhamnolipids fermentation: impact factors and fermentation strategies

Abstract

Rhamnolipids have recently attracted considerable attentions because of their excellent biosurfactant performance and potential applications in agriculture, environment, biomedicine, etc., but severe foaming causes the high cost of production, restraining their commercial production and applications. To reduce or eliminate the foaming, numerous explorations have been focused on foaming factors and fermentation strategies, but a systematic summary and discussion are still lacking. Additionally, although these studies have not broken through the bottleneck of foaming, they are conducive to understanding the foaming mechanism and developing more effective rhamnolipids production strategies. Therefore, this review focuses on the effects of fermentation components and control conditions on foaming behavior and fermentation strategies responded to the severe foaming in rhamnolipids fermentation and systematically summarizes 6 impact factors and 9 fermentation strategies. Furthermore, the potentialities of 9 fermentation strategies for large-scale production are discussed and some further strategies are suggested. We hope this review can further facilitate the understanding of foaming factors and fermentation strategies as well as conducive to developing the more effective large-scale production strategies to accelerate the commercial production process of rhamnolipids.

An overview of edible foams in food and modern cuisine: Destabilization and stabilization mechanisms and applications

“…Surfactant can be adsorbed to the gas-liquid interface to form an interfacial film, preventing the coalescence between bubbles during foam formation and finally producing smaller bubbles. The lifetime of the (Gong et al, 2021); lipopeptide (Venkataraman et al, 2021); Bacillus subtilis biosurfactant (Nitschke & Silva, 2018) • Biodegradability, low or no toxicity…”

“…Moreover, some microbial surfactants, such as rhamnolipids (Gong et al., 2021), lipopeptides (Venkataraman et al., 2021), and Bacillus subtilis biosurfactants (surfactin and iturin A) (Nitschke & Silva, 2018), have also been reported to be used in food colloid systems, but their application in foams remains to be further studied. LMWSs have the defect of insufficient interfacial strength, but they have the incomparable adsorption ability of other polymer emulsifiers due to their relatively low‐molecular weight and strong amphiphilic structure.…”

Achieving “Non-Foaming” Rhamnolipid Production and Productivity Rebounds of Pseudomonas aeruginosa under Weakly Acidic Fermentation

“…Rhamnolipids are a class of glycolipid-type biosurfactants produced primarily by Pseudomonas aeruginosa [1]. As the most studied biosurfactants, rhamnolipids not only have the properties of solubilization, emulsification, wetting, foaming, dispersion and reduction of surface tension common to surfactants, but also have the advantages of non-toxicity, biodegradability, ecological safety and high surface activity compared with other surfactants produced by chemical synthesis or petroleum refining methods [2][3][4][5][6], and they have received green certifications in the fields of pesticides and food.…”

“…However, traditional chemical defoaming methods such as the use of defoamers have been proved to be ineffective in suppressing severe foaming in rhamnolipid fermentation unless chemical defoamers are used excessively and the working volume of the fermenter is severely sacrificed. Foam fractionation fermentation, foam adsorption fermentation and fermentation-defoaming tandem systems are all ex situ and require external equipment for foam storage or defoaming, causing some other problems such as increased equipment costs, loss of biomass and media and increased contamination risks, which cannot be ignored in large-scale industrial production [1]. Anaerobic and solid fermentations are usually not feasible in the industrial production of rhamnolipids because of their remarkable low productivity [1].…”

“…Foam fractionation fermentation, foam adsorption fermentation and fermentation-defoaming tandem systems are all ex situ and require external equipment for foam storage or defoaming, causing some other problems such as increased equipment costs, loss of biomass and media and increased contamination risks, which cannot be ignored in large-scale industrial production [1]. Anaerobic and solid fermentations are usually not feasible in the industrial production of rhamnolipids because of their remarkable low productivity [1]. Therefore, submerged liquid fermentation without external equipment (in situ) is still the sole promising method for the large-scale production of rhamnolipids [12].…”