This article includes an updated review of the classification, uses and side effects of surfactants for their application in the cosmetic, personal care and pharmaceutical industries. Based on their origin and composition, surfactants can be divided into three different categories: (i) synthetic surfactants; (ii) bio-based surfactants; and (iii) microbial biosurfactants. The first group is the most widespread and cost-effective. It is composed of surfactants, which are synthetically produced, using non-renewable sources, with a final structure that is different from the natural components of living cells. The second category comprises surfactants of intermediate biocompatibility, usually produced by chemical synthesis but integrating fats, sugars or amino acids obtained from renewable sources into their structure. Finally, the third group of surfactants, designated as microbial biosurfactants, are considered the most biocompatible and eco-friendly, as they are produced by living cells, mostly bacteria and yeasts, without the intermediation of organic synthesis. Based on the information included in this review it would be interesting for cosmetic, personal care and pharmaceutical industries to consider microbial biosurfactants as a group apart from surfactants, needing specific regulations, as they are less toxic and more biocompatible than chemical surfactants having formulations that are more biocompatible and greener.

The increase of crop production along with stricter requirements on food security have augmented the demand of new and eco-friendly bactericides. Most of the bactericides used at the moment consist of persistent organic substances, representing a risk for environmental and human health. For instance, agriculture bactericides used for crop protection includes copper-based, dithiocarbamate and amide bactericides, which are not biodegradable, resulting in the necessity of further research about the production of new active principles that attack microorganisms without producing any harmful effect on human health or environment. The biosurfactant extract evaluated in this work as a bactericide, is obtained from corn steep water, a residual stream of corn wet milling industry, which is fermented spontaneously by probiotic lactic acid bacteria that possess the capacity to produce biosurfactants. In previous works, it has been demonstrated that this biosurfactant extract is able to promote the growth of Lactobacillus casei in drinkable yogurts, though its antimicrobial activity against pathogenic strains has not been evaluated at the moment. The results obtained in this work have proved that this biosurfactant extract is effective as bactericide against Pseudomonas aeruginosa and Escherichia coli, at concentrations of 1 mg/mL, opening the door to its use in agrifood formulations for reducing the use of chemical pesticides and preservatives.

In this work a Bacillus strain with capacity to produce biosurfactants was isolated from commercial corn steep water (CSW). The identification of this bacterium was based on phenotypic characteristics. This is a Gram-positive Bacillus, macroscopically catalase-negative, that possesses high mobility and forms terminal endospore. The colonies formed by the isolated Bacillus strain are characterized by a creaming, dull and glistening phenotype with a small point-like elevation in the center. Regarding its antimicrobial activity, the isolated Bacillus strain was effective against Candida albicans and Staphylococcus aureus observing, in the presence of pathogenic strains, a phenotype dissociation, switching the colonies from a whitish to yellowish pigmentation. The isolated microorganism, contrarily to other Bacillus strains, has the ability to produce extracellular and cell-bound biosurfactants. The analyses revealed that both biosurfactant extracts are similar to the lipopeptide biosurfactant produced by Bacillus subtilis. GRAPHICAL ABSTRACT López-Prieto et al., 2019

Biosurfactants are surface-active compounds that are produced by microorganisms, which in addition to their surfactant capacity, can possess interesting antimicrobial activities that are used in their incorporation into the agrifood industry. In this work, the preservative capacity of a novel biosurfactant extract obtained from a residual stream of the corn-milling industry was evaluated against two different fungi (Aspergillus brasiliensis and Candida albicans) under different biosurfactant concentrations (0.33–0.99 mg/mL), temperatures (4–40 °C), and incubation times (5–11 days). All the assays started with the same concentration of fungi (2 × 10⁶ CFU/mL). The results showed that temperature played an important role in the fungicidal and fungistatic effects of this biosurfactant extract. It was observed that at a low biosurfactant concentration (0.33 mg/mL) and at low temperatures in the range tested, this biosurfactant extract possessed an important fungicidal effect (complete inhibition) on A. brasiliensis, while at intermediate temperatures, it achieved a fungistatic effect (50% of inhibition) at the highest concentration. Regarding C. albicans, it was observed that this strain was more resistant than A. brasiliens, although it was possible to achieve growth inhibitions of 76.3% at temperatures of 40 °C after 8 days of incubation with a biosurfactant concentration of 0.99 mg/mL. This work supports the possible application of biosurfactants extracted from corn steep water as preservatives and antimicrobial agents against fungal contaminations on agrifood products.