2,5-Diketopiperazines: synthesis, reactions, medicinal chemistry, and bioactive natural products.

Diverse types of microbial surface-active amphiphilic molecules are produced by a range of microbial communities. The extraordinary properties of biosurfactant / bioemulsifier (BS/BE) as surface active products allows them to have key roles in various field of applications such as bioremediation, biodegradation, enhanced oil recovery, pharmaceutics, food processing among many others. This leads to a vast number of potential applications of these BS/BE in different industrial sectors. Despite the huge number of reports and patents describing BS and BE applications and advantages, commercialization of these compounds remain difficult, costly and to a large extent irregular. This is mainly due to the usage of chemically synthesized media for growing producing microorganism and in turn the production of preferred quality products. It is important to note that although a number of developments have taken place in the field of biosurfactant industries, large scale production remains economically challenging for many types of these products. This is mainly due to the huge monetary difference between the investment and achievable productivity from the commercial point of view. This review discusses low cost, renewable raw substrates and fermentation technology in BS/BE production processes and their role in reducing the production cost.

Cost effective technologies and renewable substrates for biosurfactants' production.

Structural and physicochemical characterization of crude biosurfactant produced by Pseudomonas aeruginosa SP4 isolated from petroleum-contaminated soil.

In recent years, heavy metals pollution is found to be a serious environmental issue and various technologies are being discovered for their cleanup from environment. The use of biosurfactants for this purpose was found to be an eco-friendly approach and also an alternate to conventional complex remediation systems. Due to their diversity, biosurfactants are considered as a potential candidate for the environmental cleanup of pollutants. Therefore, a greater attention was paid on biosurfactants and identifying their potential applications. By considering the importance of biosurfactants, the present review article presents an exhaustive evaluation of different sources of biosurfactants and also their properties and applications which is the focus of future studies.

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Biosurfactants-Types, Sources and Applications

Endophytic microbes are ubiquitous in most plant species. Endophytic microbes enter plants mainly through wounds, naturally occurring as a result of plant growth or through root hairs and at epidermal conjunctions. Besides gaining entrance to plants through natural openings or wounds, endophytic microbes appear to actively penetrate plant tissues using hydrolytic enzymes like cellulase and pectinase. Diverse community structure of endophytes can be analyzed using culture-dependent and culture-independent method. Endophytic bacteria belong to different phyla such as Acidobacteria, Actinobacteria, Ascomycota, Bacteroidetes, Basidiomycota, Deinococcus-Thermus, and Firmicutes. Endophytic archaea (Euryarchaeota) were reported using only culture-independent method. Endophytic microbes were most predominant and studied and belonged to three major phyla Actinobacteria, Proteobacteria, and Firmicutes. Among reported genera Achromobacter, Bacillus, Burkholderia, Enterobacter, Herbaspirillum, Pantoea, Pseudomonas, Rhizobium, and Streptomyces were dominant in most host plants. Along with common endophytic microbial genera, there were many niche-specific microbial genera that have been reported from different host plants. Application of associative microbes for sustainable agriculture holds immense potential. Endophytic microbes are known to enhance growth and yield of plants by fixing atmospheric nitrogen and solubilization of phosphorus, potassium, and zinc; production of phytohormones (cytokinins, auxins, and gibberellins), ammonia, hydrogen cyanide, and siderophores; and possession of antagonistic activity as well as reducing the level of stress ethylene in host plants. Endophytes seem to contribute to plant fitness and development, displaying beneficial traits that can be exploited in agricultural biotechnology. The interactions between endophytes and plants can promote plant health and play a significant role in low-input sustainable agriculture for both food and nonfood crops. This chapter summarizes part of the work being done on endophytic microbes, including their isolation, identification, diversity, distribution, and applications for sustainable agriculture.

Endophytic Microbes in Crops: Diversity and Beneficial Impact for Sustainable Agriculture

Plant growth-promoting traits of epiphytic and endophytic yeasts isolated from rice and sugar cane leaves in Thailand.

Chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste

Aims: To isolate and characterize biosurfactants produced by a thermotolerant yeast isolated in Thailand.



Materials and Results:  Yeast strains isolated from plant material in Thailand were first screened for the ability to produce lipase and biosurfactant. A strain Y12, identified as Candida ishiwadae by physiological tests, survived at 45°C and produced relatively large amounts of biosurfactants. From the culture filtrate of this strain, two glycolipid biosurfactants, a and b, were purified by solvent fractionation, silica gel and ODS column chromatographies. Compounds a and b were determined to be monoacylglycerols; 1-linoleylglycerol and 1-oleylglycerol, respectively. Both compounds exhibited higher surfactant activities tested by the drop collapse test than several artificial surfactants such as sodium dodecyl sulphate.



Conclusions:  Glycolipid biosurfactants produced by a thermotolerant yeast, C. ishiwadae were characterized to be monoacylglycerols which exhibited high surfactant activities.



Significance and Impact of the Study:  A thermotolerant yeast strain, C. ishiwadae, could be a potential candidate for producing monoacylglycerols which are useful in industrial applications.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2672.2004.02202.x

Monoacylglycerols: glycolipid biosurfactants produced by a thermotolerant yeast, Candida ishiwadae

Microbial metabolism of α-mangostin isolated from Garcinia mangostana L.

Microorganisms produce plant growth regulators, such as auxins, cytokinins and gibberellins, to promote plant growth. Auxins are a group of compounds with an indole ring that have a positive effect on plant growth. Indole-3-acetic acid (IAA) is a plant growth hormone classified as an indole derivative of the auxin family. IAA biosynthesis pathways have been reported and widely studied in several groups of bacteria. Only a few studies on IAA biosynthesis pathways have been conducted in yeast. This study aimed to investigate IAA biosynthesis pathways in a basidiomycetous yeast (Rhodosporidium paludigenum DMKU-RP301). Investigations were performed both with and without a tryptophan supplement. Indole compound intermediates were detected by gas chromatography-mass spectrometry. Indole-3-lactic acid and indole-3-ethanol were found as a result of the enzymatic reduction of indole-3-pyruvic acid and indole-3-acetaldehyde, in IAA biosynthesis via an indole-3-pyruvic acid pathway. In addition, we also found indole-3-pyruvic acid in culture supernatants determined by high-performance liquid chromatography. Identification of tryptophan aminotransferase activity supports indole-3-pyruvic acid-routed IAA biosynthesis in R. paludigenum DMKU-RP301. We hence concluded that R. paludigenum DMKU-RP301 produces IAA through an indole-3-pyruvic acid pathway.

Panarat Arunrattiyakorn

Papers

Plant growth-promoting traits of epiphytic and endophytic yeasts isolated from rice and sugar cane leaves in Thailand.

Chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste

Monoacylglycerols: glycolipid biosurfactants produced by a thermotolerant yeast, Candida ishiwadae

Microbial metabolism of α-mangostin isolated from Garcinia mangostana L.

Indole-3-acetic acid biosynthetic pathways in the basidiomycetous yeast Rhodosporidium paludigenum.