Encarnación Jurado Alameda

Performance of a biosurfactant produced by a Bacillus subtilis strain isolated from crude oil samples as compared to commercial chemical surfactants

In this work, the biosurfactant produced by a Bacillus subtilis strain isolated from crude oil samples was characterized and its properties compared with commercially available chemical surfactants. The purified biosurfactant production yield (Y(P/X)) was 0.20 g/gcell dry weight. The surface tension (29.0 mN/m) and critical micelle concentration (40 mg/l) were found to be similar to the values previously reported for surfactin. Temperature and pH stability of the biosurfactant were also evaluated. The biosurfactant was exposed to different temperatures (20, 37 and 46°C) during two weeks and was found to be as stable as the commercial chemical surfactants Glucopone(®)215, Glucopone(®)650, Findet(®)1214N/23 and linear alkylbenzene sulfonates (LAS). Moreover, the biosurfactant subjected to 121°C for 20 min did not exhibit a significant loss of surface activity. Contrary to the commercial chemical surfactants that were found to be stable over a wide range of pH (3.0-10.0), the biosurfactant was unstable precipitating at pH values below 5.0. The emulsification indexes showed that the biosurfactant possesses equal or superior capacity to form emulsions with n-hexadecane as compared to the commercial chemical surfactants. Moreover, the anti-adhesive activity of the biosurfactant and commercial chemical surfactants was evaluated. The biosurfactant showed some activity against Staphylococcus aureus and Escherichia coli. Nevertheless, no particular trend or special effect could be assigned to the use of commercial chemical surfactants as anti-adhesives. Results gathered in this work suggest that the biosurfactant recovered from B. subtilis EG1 constitutes an interesting alternative to the commercial chemical surfactants with potential use in several industries.

Rhamnolipid and surfactin production from olive oil mill waste as sole carbon source

Olive mill waste (OMW) creates a major environmental problem due to the difficulty of further waste processing. In this work we present an approach to give OMW added value by using it for the production of biosurfactants. Two bacterial species, Pseudomonas aeruginosa and Bacillus subtilis, were grown with OMW as the sole carbon source. Glycerol and waste frying oil were used as comparative carbon sources. B. subtilis produced surfactin (a lipopeptide) at a maximum concentration of 3.12 mg/L with 2% w/v of OMW in the medium, dropping to 0.57 mg/L with 10% w/v of OMW. In contrast, P. aeruginosa produced 8.78 mg/L of rhamnolipid with 2% w/v OMW increasing to 191.46 mg/L with 10% w/v OMW. The use of solvent-extracted OMW reduced the biosurfactant production by 70.8% and 88.3% for B. subtilis and P. aeruginosa respectively. These results confirm that OMW is a potential substrate for biosurfactant production.

Modification of the activity of an a-amylase from Bacillus licheniformis by several surfactants

The influence of different commercial surfactants on the enzymatic activity of a commercial α-amylase from Bacillus licheniformis (Termamyl 300 L) has been studied. As non-ionic surfactants, alkyl polyglycosides (Glucopon® 215, Glucopon® 600 and Glucopon® 650) were studied, as were fatty alcohol ethoxylates (Findet 1214N/23 and Findet 10/15), and nonyl phenol ethoxylate (Findet 9Q/21.5NF). Also, an anionic surfactant, linear alkyl benzene sulfonate (LAS) was assayed. In general, none of the non-ionic surfactants studied, except Findet 10/15, vary substantially the enzymatic activity. Findet 10/15 has the strongest hydrophobic character and reduces the enzymatic activity more significantly the greater its concentration. Regarding LAS, this surfactant significantly depressed enzymatic activity, presumably due to the electrostatic interactions caused by its anionic character.

Hydrolysis of olive mill waste to enhance rhamnolipids and surfactin production

The aim of this work was to demonstrate the effectiveness of hydrolysis pretreatment of olive mill (OMW) waste before use as a carbon source in biosurfactant production by fermentation. Three hydrolysis methods were assessed: enzymatic hydrolysis, acid pretreatment plus enzymatic hydrolysis, and acid hydrolysis. Fermentation was carried out using two bacterial species: Pseudomonas aeruginosa and Bacillus subtilis. Our results showed that the enzymatic hydrolysis was the best pretreatment, yielding up to 29.5 and 13.7mg/L of rhamnolipids and surfactins respectively. Glucose did not show significant differences in comparison to enzymatically hydrolysed OMW. At the best conditions found rhamnolipids and surfactins reached concentrations of 299 and 26.5mg/L; values considerably higher than those obtained with non-hydrolysed OMW. In addition, enzymatic pretreatment seemed to partially reduce the inhibitory effects of OMW on surfactin production. Therefore, enzymatic hydrolysis proved to effectively increase the productivity of these biosurfactants using OMW as the sole carbon source.

Design of Experiments to Evaluate the Detergency of Surfactants on Fatty Soils in a Continuous-Flow Device

Detersive processes are complex systems involving a great number of variables. To determine the effect of these variables on the washing of hard surfaces and fatty soils is the object of this work. The statistical design of experiments has been used to evaluate the influence of factors such as temperature, soil concentration and surfactant concentration on detergency. The experimental trials have been made in a continuous-flow device where the soiling agent is confined in a column filled with borosilicate glass spheres. Solutions of the commercial surfactant Berol© LFG61 (a mixture of alkylpolyglucosides and fatty-alcohol ethoxylates) have been employed as the wash bath. Both the design of experiments and the continuous experimental system used proved to be an effective tool for detecting the key variables in the cleaning process. Expressions were developed to simulate detergency levels as a function of the variables assayed, always inside the experimental domain. In the trials with oleic acid as the soiling agent, it was found that the temperature and soil concentration were the most important variables to take into account, while the surfactant concentration was not a significant variable. When a semi-solid mixture of different fatty acids was employed, all the variables assayed proved significant, with high detergency values being reached by combining temperature and surfactant concentrations. Results clearly show that the effectiveness of the surfactant used is influenced by the type and concentration of the soil and thus the intended application of the product being developed should be taken into account when designing detergent formulas.

Modification of the activity of an alpha-amylase from Bacillus licheniformis by several surfactants

The influence of different commercial surfactants on the enzymatic activity of a commercial α-amylase from Bacillus licheniformis (Termamyl 300 L) has been studied. As non-ionic surfactants, alkyl polyglycosides (Glucopon® 215, Glucopon® 600 and Glucopon® 650) were studied, as were fatty alcohol ethoxylates (Findet 1214N/23 and Findet 10/15), and nonyl phenol ethoxylate (Findet 9Q/21.5NF). Also, an anionic surfactant, linear alkyl benzene sulfonate (LAS) was assayed. In general, none of the non-ionic surfactants studied, except Findet 10/15, vary substantially the enzymatic activity. Findet 10/15 has the strongest hydrophobic character and reduces the enzymatic activity more significantly the greater its concentration. Regarding LAS, this surfactant significantly depressed enzymatic activity, presumably due to the electrostatic interactions caused by its anionic character.

Cleaning of Starchy Soils in Clean-in-Place (CIP) Systems: Relationship Between Contact Angle and Detergency

The cleaning of hard surfaces soiled with starch films using nonionic (alkylpolyglucosides and polyoxyethylene alkyl ethers) and zwitterionic (lauramine oxide) surfactant solutions has been investigated. Response surface methodology was applied to determine the effect of the composition of the cleaning solution on detergency, as well as the relationship between the contact angle of surfactant solutions on starch films and the removal efficacy of such films. The surfactants with a higher capacity for the removal of starch films were lauramine oxide and alkylpolyglucosides, and their mixtures. The effect of polyoxyethylene alkyl ethers was also statistically significant; however, their contribution to soil removal was very low. A correlation between contact angle and detergency for starchy soils was found, and the importance of the hydration process of the starch film on its removal was established.The cleaning of hard surfaces soiled with starch films using nonionic (alkylpolyglucosides and polyoxyethylene alkyl ethers) and zwitterionic (lauramine oxide) surfactant solutions has been investigated. Response surface methodology was applied to determine the effect of the composition of the cleaning solution on detergency, as well as the relationship between the contact angle of surfactant solutions on starch films and the removal efficacy of such films. The surfactants with a higher capacity for the removal of starch films were lauramine oxide and alkylpolyglucosides, and their mixtures. The effect of polyoxyethylene alkyl ethers was also statistically significant; however, their contribution to soil removal was very low. A correlation between contact angle and detergency for starchy soils was found, and the importance of the hydration process of the starch film on its removal was established. GRAPHICAL ABSTRACT