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.

Synthesis of biosurfactants and their advantages to microorganisms and mankind.

Biosurfactants are surface-active compounds synthesized by a wide variety of microorganisms. They are molecules that have both hydrophobic and hydrophilic domains and are capable of lowering the surface tension and the interfacial tension of the growth medium. Biosurfactants possess different chemical structures--lipopeptides, glycolipids, neutral lipids and fatty acids. They are nontoxic biomolecules that are biodegradable. Biosurfactants also exhibit strong emulsification of hydrophobic compounds and form stable emulsions. The low water solubility of these hydrophobic compounds limits their availability to microorganisms, which is a potential problem for bioremediation of contaminated sites. Microbially produced surfactants enhance the bioavailability of these hydrophobic compounds for bioremediation. Therefore, biosurfactant-enhanced solubility of pollutants has potential applications in bioremediation. Not only are the biosurfactants useful in a variety of industrial processes, they are also of vital importance to the microbes in adhesion, emulsification, bioavailability, desorption and defense strategy. These interesting facts are discussed in this chapter.

Loss of AMPK exacerbates experimental autoimmune encephalomyelitis disease severity.

AMP-activated protein kinase (AMPK) is an energy sensing metabolic switch in mammalian cells. Here, we report our novel finding that AMPK is lost in all immune cells of experimental autoimmune encephalomyelitis (EAE), an inflammatory disease of Central Nervous System (CNS). AMPKalpha1 is predominantly expressed in T cells and antigen presenting cells (APCs), which are primarily involved in EAE disease progression. AMPK is lost at protein level in spleen macrophages, total T cells and their subsets (CD4, CD8 and regulatory T cells) isolated from EAE afflicted animals compared to control, without affecting its mRNA levels suggesting that the loss of AMPK protein is the result of posttranscriptional modification. To examine its pathological relevance in inflammatory disease, EAE was induced in wild type (+/+) and AMPKalpha1 null mice (-/-) using MOG(35-55) peptide. AMPKalpha1(-/-) mice exhibited severe EAE disease with profound infiltration of mononuclear cells compared to wild type mice however, AMPKalpha2 is not involved in enhancing the severity of the disease. Spleen cells isolated from AMPKalpha1(-/-) immunized mice exhibited a significant induction in the production of IFNgamma. Our study identifies AMPK as a down regulated target during disease in all immune cells and possibly restoring AMPK may serve as a novel therapeutic target in autoimmune diseases like multiple sclerosis (MS).

Molecular organization of peroxisomal enzymes: protein-protein interactions in the membrane and in the matrix.

The beta-oxidation of fatty acids in peroxisomes produces hydrogen peroxide (H2O2), a toxic metabolite, as a bi-product. Fatty acids beta-oxidation activity is deficient in X-linked adrenoleukodystrophy (X-ALD) because of mutation in ALD-gene resulting in loss of very long chain acyl-CoA synthetase (VLCS) activity. It is also affected in disease with catalase negative peroxisomes as a result of inactivation by H2O2. Therefore, the following studies were undertaken to delineate the molecular interactions between both the ALD-gene product (adrenoleukodystrophy protein, ALDP) and VLCS as well as H2O2 degrading enzyme catalase and proteins of peroxisomal beta-oxidation. Studies using a yeast two hybrid system and surface plasmon resonance techniques indicate that ALDP, a peroxisomal membrane protein, physically interacts with VLCS. Loss of these interactions in X-ALD cells may result in a deficiency in VLCS activity. The yeast two-hybrid system studies also indicated that catalase physically interacts with L-bifunctional enzyme (L-BFE). Interactions between catalase and L-BFE were further supported by affinity purification, using a catalase-linked resin. The affinity bound 74-kDa protein, was identified as L-BFE by Western blot with specific antibodies and by proteomic analysis. Additional support for their interaction comes from immunoprecipitation of L-BFE with antibodies against catalase as a catalase- L-BFE complex. siRNA for L-BFE decreased the specific activity and protein levels of catalase without changing its subcellular distribution. These observations indicate that L-BFE might help in oligomerization and possibly in the localization of catalase at the site of H2O2 production in the peroxisomal beta-oxidation pathway.

Reductive dechlorination of tetrachloroethene by a mixed bacterial culture growing on ethyl lactate.

Chloroethenes like tetrachloroethene (PCE) are the most prevalent groundwater contaminants in the USA. Their presence as nonaqueous phase liquids (NAPLs) makes remediation difficult. Among options for NAPL cleanup, co-solvent injection has demonstrated success. However, the process has the potential to leave considerable residue of the co-solvent as well as residual chloroethene. Our rationale in this study was to examine whether this residual solvent could be a potential electron donor for the remediation of the residual chloroethene. We hypothesized that ethyl lactate, a "green" solvent, could serve both as a NAPL extraction solvent and an electron donor for reductive dechlorination of residual chloroethene. We examined whether a mixed culture known to degrade PCE with lactate could also grow on ethyl lactate and whether it could stimulate PCE dechlorination. Biomass growth and PCE dechlorination were observed by protein and chloride production, respectively, in the culture; with a specific dechlorination rate of 50 150 microg (mg cell d)(-1). Ethyl lactate abiotically breaks down to ethanol and lactate, the latter being a rich source of hydrogen fo reductive dechlorination. The results demonstrate that ethyl lactate may be promising for in situ bioremediation following NAPL extraction.

Recent applications of biosurfactants as biological and immunological molecules.

The interest in microbial biosurfactants has steadily increased during the past decade. In addition to the classical application as emulsifiers of hydrocarbons, they can be used in environmental protection, crude-oil recovery, food-processing industries and in various fields of biomedicine. Biosurfactants have several advantages over chemical surfactants including lower toxicity and higher biodegradability, and are likely to become molecules of the future in areas such as biomedicine and therapeutics. Here, we discuss the role and applications of biosurfactants (mainly glycolipids and lipopeptides) focusing on medicinal and therapeutic perspectives.

Comparison of synthetic surfactants and biosurfactants in enhancing biodegradation of polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbon (PAH) contamination of the environment represents a serious threat to the health of humans and ecosystems. Given the human health effects of PAHs, effective and cost-competitive remediation technologies are required. Bioremediation has shown promise as a potentially effective and low-cost treatment option, but concerns about the slow process rate and bioavailability limitations have hampered more widespread use of this technology. An option to enhance the bioavailability of PAHs is to add surfactants directly to soil in situ or ex situ in bioreactors. Surfactants increase the apparent solubility and desorption rate of the PAH to the aqueous phase. However, the results with some synthetic surfactants have shown that surfactant addition can actually inhibit PAH biodegradation via toxic interactions, stimulation of surfactant degraders, or sequestration of PAHs into surfactant micelles. Biosurfactants have been shown to have many of the positive effects of synthetic surfactants but without the drawbacks. They are biodegradable and nontoxic, and many biosurfactants do not produce true micelles, thus facilitating direct transfer of the surfactant-associated PAH to bacteria. The results with biosurfactants to date are promising, but further research to elucidate surfactant-PAH interactions in aqueous environments is needed to lead to predictive, mechanistic models of biosurfactant-enhanced PAH bioavailability and thus better bioremediation design.