Stability and emulsifying capacity of biosurfactants obtained from lignocellulosic sources using Lactobacillus pentosus

Burkholderia thailandensis E264 as a promising safe rhamnolipids' producer towards a sustainable valorization of grape marcs and olive mill pomace

Within the circular economy framework, our study aims to assess the rhamnolipid production from winery and olive oil residues as low-cost carbon sources by nonpathogenic strains. After evaluating various agricultural residues from those two sectors, Burkholderia thailandensis E264 was found to use the raw soluble fraction of nonfermented (white) grape marcs (NF), as the sole carbon and energy source, and simultaneously, reducing the surface tension to around 35 mN/m. Interestingly, this strain showed a rhamnolipid production up to 1070 mg/L (13.37 mg/g of NF), with a higher purity, on those grape marcs, predominately Rha-Rha C14-C14, in MSM medium. On olive oil residues, the rhamnolipid yield of using olive mill pomace (OMP) at 2% (w/v) was around 300 mg/L (15 mg/g of OMP) with a similar CMC of 500 mg/L. To the best of our knowledge, our study indicated for the first time that a nonpathogenic bacterium is able to produce long-chain rhamnolipids in MSM medium supplemented with winery residues, as sole carbon and energy source. KEY POINTS: • Winery and olive oil residues are used for producing long-chain rhamnolipids (RLs). • Both higher RL yields and purity were obtained on nonfermented grape marcs as substrates. • Long-chain RLs revealed stabilities over a wide range of pH, temperatures, and salinities.

Advances on research in the use of agro-industrial waste in biosurfactant production

Biosurfactants are amphiphilic molecules produced by a variety of microorganisms, including bacteria, yeast and filamentous fungi. Unlike chemically synthesized surfactants, biosurfactants present advantages, such as biodegradability, low toxicity, high selectivity and activity under extreme temperature, pH and salinity conditions, as well as a low critical micelle concentration. Moreover, they can be produced from agro-industrial waste and renewable sources. Their structural diversity and functional properties mean that they have potential applications in various industrial processes as wetting agents, dispersants, emulsifiers, foaming agents, food additives and detergents, as well as in the field of environmental biotechnology. However, opportunities for their commercialization have been limited due to the low yields obtained in the fermentation processes involved in their production as well as the use of refined raw materials, which means higher cost in production. In an attempt to solve these limitations on the commercialization of biosurfactants, various research groups have focused on testing the use of inexpensive alternative sources, such as agro-industrial waste, as substrates for the production of different biosurfactants. In addition to enabling the economical production of biosurfactants, the use of such waste aims to reduce the accumulation of compounds that cause environmental damage. This review shows advances in biosurfactant production carried out using different waste materials or by-products from agro-industrial activities.

Inhibition of pathogenic bacterial biofilms on PDMS based implants by L. acidophilus derived biosurfactant

Background

Lactobacillus spp. predominantly shows its presence as a normal mucosal flora of the mouth and intestine. Therefore, the objective of our research is to investigate the in-vitro conditions for the prospective of medically valuable biosurfactants (BSs) derived from Lactobacillus spp. Biosurfactant (BS) obtained from Lactobacillus spp. exhibit antibiofilm and antiadhesive activity against broad range of microbes. In the present study we investigated the production, purification and properties of key components of the cell-associated-biosurfactant (CABS) from Lactobacillus acidophilus NCIM 2903.

Results

Extracted, purified, freeze-dried CABS shows reduction in surface tension (SFT) of phosphate buffer saline (PBS @pH 7.0) from 71 to 26 mN/m and had a critical micelle concentration (CMC) of 23.6 mg/mL. The CABS showed reduction in interfacial tension (IFT) against various hydrocarbons and had effective spreading capability as reflected through the decrease in contact angle (CA) on different surfaces (polydimethylsiloxane - PDMS, Teflon tape, glass surface, polystyrene film and OHP sheet). The anionic nature of CABS displayed stability at different pH and temperatures and formed stable emulsions. Thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR) revealed CABS as glycolipoprotein type. The Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE) showed presence of multiple bands in a molecular range of 14.4 to 60 kDa, with prominent bands of 45 kDa. The CABS has significant antiadhesion and antibiofilm activity against tested bacterial strains.

Conclusion

The current challenging situation is to develop methods or search for the molecules that will prevent the formations of biofilm on medical bioimplants of PDMS based materials. These findings are supportive for the use of Lactobacilli derived BS as potential antiadhesive agent on various surfaces of biomedical devices.

Study of the synergic effect between mica and biosurfactant to stabilize Pickering emulsions containing Vitamin E using a triangular design

HYPOTHESIS

Vitamin E has interesting biological functions for the cosmetic and pharmaceutical industry because it can act as a fat-soluble antioxidant, as well as peroxyl radical scavenger. However, this vitamin is formed by a group of compounds that include tocopherols (γ-tocopherols, α-tocopherol) characterized by their poor solubility in water, what implies the need of using stabilizing agents such as biosurfactants or minerals, in order to make them soluble or stable in formulations composed by water and oil.

EXPERIMENTS

In this work, it has been evaluated the synergic effect between a mining silicate mineral (mica) and a biosurfactant extract, obtained from corn steep liquor, to stabilize emulsions containing water and a non-aqueous soluble antioxidant consisting of Vitamin E, through the use of a triangular design.

FINDINGS

The results show that the presence of biosurfactant extract improves the emulsion volume up to 70% after 22 days, for an emulsion composed of Vitamin E and biosurfactant, whereas the mica component was able to increase the emulsion stability until values of 80% after 30 days of experiment, for those emulsions containing 10% of mica. Hence, both novel ingredients produce a synergistic effect on the Pickering emulsions carried out in the study.

Biological Surfactants vs. Polysorbates: Comparison of Their Emulsifier and Surfactant Properties

In this work two biological surfactants, a cell-bound biosurfactant produced by Lactobacillus pentosus and a biosurfactant obtained from a fermented stream corn milling industry, were compared with two chemical surfactants (polysorbate 20 and polysorbate 80) in terms of surface tension reduction, critical micellar concentration (CMC), oil spreading and emulsifying capacity. Biological surfactants showed a similar ability to reduce the surface tension of water as polysorbates, which was in conformance with the results obtained in the drop collapse test. Regarding the ability to spread the oil on water, both biosurfactants produced similar results as polysorbates after 1 h. However, after 24 h, polysorbates and biosurfactant from corn stream were more effective than L. pentosus biosurfactant, producing greater free oil areas. Concerning the emulsifying activity, in terms of relative emulsion volume (EV), the biosurfactant produced from L. pentosus gave the best results (EV = 100%), after 1 day of emulsion formation, keeping this value over 50% after 15 days of emulsion formation; whereas polysorbates gave EV values lower than 50%. The CMC values of the biosurfactant from corn stream and of polysorbates were closer in comparison with the CMC value of L. pentosus biosurfactant, observing that the characteristics and properties of the biosurfactant from corn stream are more similar to polysorbates than to L. pentosus biosurfactant. Thus, it could be speculated that biosurfactant from corn stream would be a good substitute for polysorbates.

Microbial production of rhamnolipids using sugars as carbon sources

Rhamnolipids are a class of biosurfactants with effective surface-active properties. The high cost of microbial production of rhamnolipids largely affects their commercial applications. To reduce the production post, research has been carried out in screening more powerful strains, engineering microbes with higher biosurfactant yields and exploring cheaper substrates to reduce the production cost. Extensive refining is required for biosurfactant production using oils and oil-containing wastes, necessitating the use of complex and expensive biosurfactant recovery methods such as extraction with solvents or acid precipitation. As raw materials normally can account for 10-30% of the overall production cost, sugars have been proven to be an alternative carbon source for microbial production of rhamnolipids due to its lower costs and straightforward processing techniques. Studies have thus been focused on using tropical agroindustrial crop residues as renewable substrates. Herein, we reviewed studies that are using sugar-containing substrates as carbon sources for producing rhamnolipids. We speculate that sugars derived from agricultural wastes rich in cellulose and sugar-containing wastes are potential carbon sources in fermentation while challenges still remain in large scales.

Sustainable wineries through waste valorisation: A review of grape marc utilisation for value-added products

Grapes are one of the most cultivated fruits worldwide, with one third of total production used in winemaking. Both red and white winemaking processes result in substantial quantities of solid organic waste, such as grape marc (pomace) and stalks, which requires suitable disposal. Grape marc accounts for approximately 10-30% of the mass of grapes crushed and contains unfermented sugars, alcohol, polyphenols, tannins, pigments, and other valuable products. Being a natural plant product rich in lignocellulosic compounds, grape marc is also a promising feedstock for renewable energy production. However, despite grape marc having such potential, advanced technologies to exploit this have not been widely adopted in wineries and allied industries. This review covers opportunities beyond traditional composting and animal feed, and examines value-added uses via the extraction of useful components from grape marc, as well as thermochemical and biological treatments for energy recovery, fuel or beverage alcohol production, and specialty novel products and applications such as biosurfactants and environmental remediation. New advances in relevant technology for each of these processes are discussed, and future directions proposed at both individual producer and regional facility scales, including advanced processing techniques for integrated ethanol production followed by bioenergy generation from the spent marc.

Biological and physicochemical properties of biosurfactants produced by Lactobacillus jensenii P6A and Lactobacillus gasseri P65

Background

Lactobacillus species produce biosurfactants that can contribute to the bacteria’s ability to prevent microbial infections associated with urogenital and gastrointestinal tracts and the skin. Here, we described the biological and physicochemical properties of biosurfactants produced by Lactobacillus jensenii P_6A and Lactobacillus gasseri P₆₅.

Results

The biosurfactants produced by L. jensenii P_6A and L. gasseri P₆₅ reduced the water surface tension from 72 to 43.2 mN m⁻¹ and 42.5 mN m⁻¹ as their concentration increased up to the critical micelle concentration (CMC) values of 7.1 and 8.58 mg mL⁻¹, respectively. Maximum emulsifying activity was obtained at concentrations of 1 and 5 mg mL⁻¹ for the P_6A and P₆₅ strains, respectively. The Fourier transform infrared spectroscopy data revealed that the biomolecules consist of a mixture of carbohydrates, lipids and proteins. The gas chromatography-mass spectrum analysis of L. jensenii P_6A biosurfactant showed a major peak for 14-methypentadecanoic acid, which was the main fatty acid present in the biomolecule; conversely, eicosanoic acid dominated the biosurfactant produced by L. gasseri P₆₅. Although both biosurfactants contain different percentages of the sugars galactose, glucose and ribose; rhamnose was only detected in the biomolecule produced by L. jensenii P_6A. Emulsifying activities were stable after a 60-min incubation at 100 °C, at pH 2–10, and after the addition of potassium chloride and sodium bicarbonate, but not in the presence of sodium chloride. The biomolecules showed antimicrobial activity against clinical isolates of Escherichia coli and Candida albicans, with MIC values of 16 µg mL⁻¹, and against Staphylococcus saprophyticus, Enterobacter aerogenes and Klebsiella pneumoniae at 128 µg mL⁻¹. The biosurfactants also disrupted preformed biofilms of microorganisms at varying concentrations, being more efficient against E. aerogenes (64%) (P_6A biosurfactant), and E. coli (46.4%) and S. saprophyticus (39%) (P₆₅ biosurfactant). Both strains of lactobacilli could also co-aggregate pathogens.

Conclusions

This report presents the first characterization of biosurfactants produced by L. jensenii P_6A and L. gasseri P₆₅. The antimicrobial properties and stability of these biomolecules indicate their potential use as alternative antimicrobial agents in the medical field for applications against pathogens that are responsible for infections in the gastrointestinal and urogenital tracts and the skin.

Novel cosmetic formulations containing a biosurfactant from Lactobacillus paracasei

Cosmetic and personal care products including toothpaste, shampoo, creams, makeup, among others, are usually formulated with petroleum-based surfactants, although in the last years the consume trend for "green" products is inducing the replacement of surface-active agents in these formulations by natural surfactants, so-called biosurfactants. In addition to their surfactant capacity, many biosurfactants can act as good emulsifiers, which is an extra advantage in the preparation of green cosmetic products. In this work, a biosurfactant obtained from Lactobacillus paracasei was used as a stabilizing agent in oil-in-water emulsions containing essential oils and natural antioxidant extract. In the presence of biosurfactant, maximum percentages of emulsion volumes (EV=100%) were observed, with droplets sizes about 199nm. These results were comparable with the ones obtained using sodium dodecyl sulfate (SDS), a synthetic well known surfactant with high emulsify capacity. Moreover, the biosurfactant and emulsions cytotoxicity was evaluated using a mouse fibroblast cell line. Solutions containing 5g/L of biosurfactant presented cell proliferation values of 97%, whereas 0.5g/L of SDS showed a strong inhibitory effect. Overall, the results herein gathered are very promising towards the development of new green cosmetic formulations.

Biosurfactants in cosmetic formulations: trends and challenges

Cosmetic products play an essential role in everyone's life. People everyday use a large variety of cosmetic products such as soap, shampoo, toothpaste, deodorant, skin care, perfume, make-up, among others. The cosmetic industry encompasses several environmental, social and economic impacts that are being addressed through the search for more efficient manufacturing techniques, the reduction of waste and emissions and the promotion of personal hygiene, contributing to an improvement of public health and at the same time providing employment opportunities. The current trend among consumers is the pursuit for natural ingredients in cosmetic products, as many of these products exhibit equal, better or additional benefits in comparison with the chemical-based products. In this sense, biosurfactants are natural compounds with great potential in the formulation of cosmetic products given by their biodegradability and impact in health. Indeed, many of these biosurfactants could exhibit a "prebiotic" character. This review covers the current state-of-the-art of biosurfactant research for cosmetic purposes and further discusses the future challenges for cosmetic applications.

Biosurfactant/s from Lactobacilli species: Properties, challenges and potential biomedical applications

Lactic acid bacteria are generally believed to have positive roles in maintaining good health and immune system in humans. A number of Lactobacilli spp. are known to produce important metabolites, among which biosurfactants in particular have shown antimicrobial activity against several pathogens in the intestinal tract and female urogenital tract partly through interfering with biofilm formation and adhesion to the epithelial cells surfaces. Around 46 reports are documented on biosurfactant production from Lactobacillus spp. of which six can be broadly classified as cell free biosurfactant and 40 as cell associated biosurfactants and only approximately 50% of those have reported on the structural composition which, in order of occurrence were mainly proteinaceous, glycolipidic, glycoproteins, or glycolipopeptides in nature. Due to the proteinaceous nature, most biosurfactant produced by strains of Lactobacillus are generally believed to be surlactin type with high potential toward impeding pathogens adherence. Researchers have recently focused on the anti-adhesive and antibiofilm properties of Lactobacilli-derived biosurfactants. This review briefly discusses the significance of Lactobacilli-derived biosurfactants and their potential applications in various fields. In addition, we highlight the exceptional prospects and challenges in fermentation economics of Lactobacillus spp.-derived biosurfactants' production processes.

Antimicrobial and anti-adhesive activities of cell-bound biosurfactant from Lactobacillus agilis CCUG31450

Lactobacillus agilisCCUG31450 produces a cell-bound biosurfactant (glycoprotein) which exhibits anti-adhesive and antimicrobial activities againstStaphylococcus aureus.

Optimization of extraction conditions and fatty acid characterization of Lactobacillus pentosus cell-bound biosurfactant/bioemulsifier

BACKGROUND

There is currently much interest in the use of natural biosurfactants and bioemulsifiers, mainly in the cosmetic, pharmaceutical and food industries. However, there are no studies on the optimization of the extraction conditions of cell-bound biosurfactants. In this work, a biosurfactant with emulsifier properties was extracted from Lactobacillus pentosus cells, under different extraction conditions, and characterized.

RESULTS

During extraction, the most influential independent variable, concerning the emulsifying capacity of biosurfactant, was the operation time, followed by temperature and salt concentration. Biosurfactant from L. pentosus was evaluated by Fourier transform infrared spectroscopy and the composition of fatty acids was analyzed by gas chromatography-mass spectrometry. The hydrophobic chain of the biosurfactant from L. pentosus comprises 548 g kg(-1) linoelaidic acid (C18:2), 221 g kg(-1) oleic or elaidic acid (C18:1), 136 g kg(-1) palmitic acid (C16) and 95 g kg(-1) stearic acid (C18). In addition, emulsions of water and rosemary oil were stabilized with a biosurfactant produced by L. pentosus and compared with emulsions stabilized with polysorbate 20.

CONCLUSION

The optimum extraction conditions of biosurfactant were achieved at 45 °C at 120 min and using 9 g kg(-1) of salt. In all the assays biosurfactant from L. pentosus yielded more stable emulsions and higher emulsion volumes than polysorbate 20.

Probiotics and its functionally valuable products-a review

During the past two decades probiotic bacteria have been increasingly proposed as health promoting bacteria in variety of food system, because of its safety, functional, and technological characteristics. Commonly, Lactobacillus spp., Bifidobacterium spp., Saccharomyces boulardii, and some other microorganisms have been considered as probiotic strains. Possibly these bacterial strains exerted several beneficial effects into gastrointestinal tract of host while administered with variety of food system. Lactic acid bacteria (LAB) usually produce antimicrobial substances like bacteriocin which have broad spectrum of antagonist effect against closely related Gram positive and Gram negative pathogens. LAB strains often produce polymeric substances such as exopolysaccharides (EPS) which increase the colonization of probiotic bacteria by cell-cell interactions in gastrointestinal tract. LAB also produces biosurfactant which showed that the wide range of antimicrobial activity against bacterial pathogen as well as its antiadhesive properties reduces the adhesion of pathogens into gastric wall membrane. Furthermore, LAB strains have also been reported for production of antioxidants which are ability to scavenge the free radicals such as superoxide anions and hydroxyl radicals. For this sense, this review article is mainly focused on the ecology, biosynthesis, genetics, target sites, and applications of bacteriocins and EPS from LAB strains. Moreover, this review discusses about the production and functions of nutritive essential element folate and iron chelating agent such as siderophores from LAB.

Evaluation and functional characterization of a biosurfactant produced by Lactobacillus plantarum CFR 2194

The study details the investigations on the ability of Lactobacillus plantarum CFR 2194, an isolate from kanjika, a rice-based ayurvedic fermented product, to produce biosurfactant. Surfactant production, as a function of fermentation time, indicates that the maximum production occurred at 72 h under stationary conditions. Isolation, partial purification, and characterization of the biosurfactant produced have been carried out, and Fourier transform infrared spectroscopy (FTIR) spectra demonstrated that biosurfactants were constituted by protein and polysaccharide fractions, i.e., possessed the structure typical of glycoprotein, which is affected by the medium composition and the phase of growth of the biosurfactant-synthesizing strain. Critical micelle concentration (cmc) of the biosurfactant was found to be 6 g l(-1). The emulsification index (EI), emulsification activity (EA), and emulsion stability (ES) values of the biosurfactant have confirmed its emulsification property. Aqueous fractions of the produced biosurfactant exhibited a significant antimicrobial activity against the food-borne pathogenic species: Escherichia coli ATCC 31705, E. coli MTCC 108, Salmonella typhi, Yersinia enterocolitica MTCC 859, and Staphylococcus aureus F 722. More importantly, the biosurfactant from L. plantarum showed antiadhesive property against above food-borne pathogens. The results thus indicate the potential for developing strategies to prevent microbial colonization of food contact surfaces and health-care prosthesis using these biosurfactants.

Evaluation of biosurfactant obtained from Lactobacillus pentosus as foaming agent in froth flotation

This study analyzes the kinetics of sediment sorption on two chemical surfactants (Tween 20 and SDS) and a biotechnologically produced surfactant (obtained from Lactobacillus pentosus). Biosurfactants were produced by fermentation of hemicellulosic sugars from vineyard pruning waste supplied as a substrate to L. pentosus. Results obtained showed that almost no SDS was adsorbed onto the sediments, whereas Tween 20 and biosurfactants from L. pentosus were absorbed after a few minutes. Kinetic models revealed that adsorption of surfactant onto riverbed sediments is governed not only by an intra-particle diffusion model (evaluated by the Weber and Morris model), but also by surface reaction models (evaluated by first, second, third order equations and Elovich equation), showing the best fit when employing the Elovich model. The adsorption properties showed by biosurfactant from L. pentosus onto sediments present it as a potential foaming agent in froth flotation.

Partial characterization of biosurfactant from Lactobacillus pentosus and comparison with sodium dodecyl sulphate for the bioremediation of hydrocarbon contaminated soil

The capability of a cell bound biosurfactant produced by Lactobacillus pentosus, to accelerate the bioremediation of a hydrocarbon-contaminated soil, was compared with a synthetic anionic surfactant (sodium dodecyl sulphate SDS-). The biosurfactant produced by the bacteria was analyzed by Fourier transform infrared spectroscopy (FTIR) that clearly indicates the presence of OH and NH groups, C=O stretching of carbonyl groups and NH nebding (peptide linkage), as well as CH₂–CH₃ and C–O stretching, with similar FTIR spectra than other biosurfactants obtained from lactic acid bacteria. After the characterization of biosurfactant by FTIR, soil contaminated with 7,000 mg Kg⁻¹ of octane was treated with biosurfactant from L. pentosus or SDS. Treatment of soil for 15 days with the biosurfactant produced by L. pentosus led to a 65.1% reduction in the hydrocarbon concentration, whereas SDS reduced the octane concentration to 37.2% compared with a 2.2% reduction in the soil contaminated with octane in absence of biosurfactant used as control. Besides, after 30 days of incubation soil with SDS or biosurfactant gave percentages of bioremediation around 90% in both cases. Thus, it can be concluded that biosurfactant produced by L. pentosus accelerates the bioremediation of octane-contaminated soil by improving the solubilisation of octane in the water phase of soil, achieving even better results than those reached with SDS after 15-day treatment.

Removal of sulfamethoxazole from solution by raw and chemically treated walnut shells

PURPOSE

The sorption of sulfamethoxazole, a frequently detected pharmaceutical compound in the environment, onto walnut shells was evaluated.

METHODS

The sorption proprieties of the raw sorbent were chemically modified and two additional samples were obtained, respectively HCl and NaOH treated. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric (TG/DTG) techniques were applied to investigate the effect of the chemical treatments on the shell surface morphology and chemistry. Sorption experiments to investigate the pH effect on the process were carried out between pH 2 and 8.

RESULTS

The chemical treatment did not substantially alter the structure of the sorbent (physical and textural characteristics) but modified the surface chemistry of the sorbent (acid-base properties, point of zero charge-pH(pzc)). The solution pH influences both the sorbent's surface charge and sulfamethoxazole speciation. The best removal efficiencies were obtained for lower pH values where the neutral and cationic sulfamethoxazole forms are present in the solution. Langmuir and Freundlich isotherms were applied to the experimental adsorption data for sulfamethoxazole sorption at pH 2, 4, and 7 onto raw walnut shell. No statistical difference was found between the two models except for the pH 2 experimental data to which the Freundlich model fitted better.

CONCLUSION

Sorption of sulfamethoxazole was found to be highly pH dependent in the entire pH range studied and for both raw and treated sorbent.

Study of the synergistic effects of salinity, pH, and temperature on the surface-active properties of biosurfactants produced by Lactobacillus pentosus

Many studies have investigated the effects of pH, temperature, and salinity on the surface-active properties of various surfactants, although in most cases the variables have been studied separately, without considering the effects of any interactions between them. In the present study, a Box-Behnken factorial design was applied to study the effects of pH, temperature, and salinity on the surface-active properties of a biosurfactant produced by Lactobacillus pentosus. The data obtained enabled development of a second-order model describing the interrelationships between operational and experimental variables, by equations including linear, interaction, and quadratic terms. The variable that had the greatest effect on the surface-active properties of the biosurfactant was pH. Moreover, at pH 3-5.5, decreases in salinity and temperature acted synergistically, reducing the surface tension of the biosurfactant; at pH 8, the same effect was observed with increasing salinity and temperature.

Valorization of winery waste vs. the costs of not recycling

Wine production generates huge amounts of waste. Before the 1990s, the most economical option for waste removal was the payment of a disposal fee usually being of around 3000 Euros. However, in recent years the disposal fee and fines for unauthorized discharges have increased considerably, often reaching 30,000-40,000 Euros, and a prison sentence is sometimes also imposed. Some environmental friendly technologies have been proposed for the valorization of winery waste products. Fermentation of grape marc, trimming vine shoot or vinification lees has been reported to produce lactic acid, biosurfactants, xylitol, ethanol and other compounds. Furthermore, grape marc and seeds are rich in phenolic compounds, which have antioxidants properties, and vinasse contains tartaric acid that can be extracted and commercialized. Companies must therefore invest in new technologies to decrease the impact of agro-industrial residues on the environment and to establish new processes that will provide additional sources of income.

Advances in utilization of renewable substrates for biosurfactant production

Biosurfactants are amphiphilic molecules that have both hydrophilic and hydrophobic moieties which partition preferentially at the interfaces such as liquid/liquid, gas/liquid or solid/liquid interfaces. Such characteristics enable emulsifying, foaming, detergency and dispersing properties. Their low toxicity and environmental friendly nature and the wide range of potential industrial applications in bioremediation, health care, oil and food processing industries makes them a highly sought after group of chemical compounds. Interest in them has also been encouraged because of the potential advantages they offer over their synthetic counterparts in many fields spanning environmental, food, biomedical, petrochemical and other industrial applications. Their large scale production and application however are currently restricted by the high cost of production and by the limited understanding of their interactions with cells and with the abiotic environment. In this paper, we review the current knowledge and latest advances in the search for cost effective renewable agro industrial alternative substrates for their production.

Application of biosurfactant produced from peanut oil cake by Lactobacillus delbrueckii in biodegradation of crude oil

Lactobacillus delbrueckii cultured with peanut oil cake as the carbon source yielded 5.35 mg ml(-1) of biosurfactant production. Five sets of microcosm biodegradation experiments were carried out with crude oil as follows: set 1 - bacterial cells+crude oil, set 2 - bacterial cells+crude oil+fertilizer, set 3 - bacterial cells+crude oil+biosurfactant, set 4 - bacterial cells+crude oil+biosurfactant+fertilizer, set 5 - with no bacterial cells, fertilizer and biosurfactant (control). Maximum degradation of crude oil was observed in set 4 (75%). Interestingly, when biosurfactant and bacterial cells were used (set 3), significant oil biodegradation activity occurred and the difference between this treatment and that in set 4 was 7% higher degradation level in microcosm experiments. It is evident from the results that biosurfactants alone is capable of promoting biodegradation to a large extent without added fertilizers.

Atypical ethanol production by carbon catabolite derepressed lactobacilli

Cost effective use of lignocellulosic biomass for bio-based chemical production requires the discovery of novel strains and processes. Lactobacillus pentosus JH5XP5 is a carbon catabolite repression negative mutant which utilizes glucose and pentoses derived from lignocellulosic biomass in the media simultaneously. With a broad range of carbon substrates, L. pentosus JH5XP5 produced a significant amount of ethanol without acetate formation. The yields of ethanol were 2.0- to 2.5-fold higher than those of lactate when glucose, galactose or maltose was used either as a single carbon source or simultaneously with glucose. L. pentosus JH5XP5 was successfully used in an integrated process of simultaneous saccharification and mixed sugar fermentation of rice straw hydrolysate. During the fermentation, the enzyme activities for the saccharification of cellulose were not diminished. Moreover glucose, xylose, and arabinose sugars derived from rice straw hyrolysate were consumed concurrently as if a single carbon source existed and no sugars or cellulosic fiber remained after the fermentation.

Stabilization of kerosene/water emulsions using bioemulsifiers obtained by fermentation of hemicellulosic sugars with Lactobacillus pentosus

The results of the present study show that Lactobacillus pentosus can produce extracellular bioemulsifiers by utilizing hemicellulosic sugars from grape marc as a source of carbon. The effectiveness of these bioemulsifiers (LPEM) was studied by preparing kerosene/water (K/W) emulsions in the presence and absence of these emulsifiers. Various parameters such as relative emulsion volume (EV), stabilizing capacity (ES), viscosity, and droplet size of K/W emulsions were measured. The EV values for K/W emulsions stabilized by concentrated LPEM were approximately 74.5% after 72 h of emulsion formation, with ES values of 97%. These values were higher than those obtained with dodecyl sodium sulfate as emulsifier (EV=62.3% and ES=87.7%). Additionally, K/W emulsions stabilized by LPEM produced polydisperse emulsions containing droplets of radius between 10 and 40 μm, which were smaller than those obtained for K/W emulsions without LPEM (droplet radius=60-100 μm). Moreover, the viscosity values of the K/W emulsions without and with LPEM were approximately 236 and 495 cP, respectively.

Isolation and functional characterization of a biosurfactant produced by Lactobacillus paracasei

In this study, the crude biosurfactant produced by a Lactobacillus paracasei strain isolated in a Portuguese dairy industry was characterized. The minimum surface tension (41.8mN/m) and the critical micelle concentration (2.5mg/ml) obtained were found to be similar to the values previously reported for biosurfactants isolated from other lactobacilli. The biosurfactant was found to be stable to pH changes over a range from 6 to 10, being more effective at pH 7, and showed no loss of surface activity after incubation at 60 degrees C for 120h. Although the biosurfactant chemical composition has not been determined yet, a fraction was isolated through acidic precipitation, which exhibited higher surface activity as compared with the crude biosurfactant. Furthermore, this isolated biosurfactant showed antimicrobial and anti-adhesive activities against several pathogenic microorganisms. In addition, L. paracasei exhibited a strong autoaggregating phenotype, which was maintained after washing and resuspending the cells in PBS, meaning that this attribute must be related to cell surface components and not to excreted factors. The autoaggregation ability exhibited by this strain, together with the antimicrobial and anti-adhesive properties observed for this biosurfactant opens the possibility for its use as an effective probiotic strain.

Reduction of water repellence of hydrophobic plant substrates using biosurfactant produced from hydrolyzed grape marc

This work demonstrates that the biosurfactant produced by Lactobacillus pentosus from grape marc hydrolysates can be successfully employed in reducing the water repellence of hydrophobic substrates, rather than chemical surfactants, as it can be produced from low-cost residual materials and it is less toxic than chemical surfactants. The method employed to measure the water repellence of the 11 plant substrates, consisting of pine bark, peat, and composts from various origins (biodegradable fraction of municipal solid waste, green waste, sewage sludge, manure, pine bark, and grape marc), was the molarity of ethanol droplet method (MED). Peat, pine bark, and the composts obtained from grape marc and pine bark were severely hydrophobic, having contact angles over 104 degrees , whereas the composts from municipal solid waste were less hydrophobic, with contact angles under 101 degrees . When hydrophobic substrates were treated with the biosurfactant from L. pentosus, the water repellence of the plant substrates was reduced in all but two cases (the least hydrophobic composts), achieving in most of the cases results better than those obtained using chemical surfactants.