Drug delivery applications and future prospects of microbial exopolysaccharides.

Over the years, exopolysaccharides (EPSs) have been utilized in various areas of research, including health, industry, environment, and agriculture, due to their flexible physical, chemical and structural properties that can be readily modified to suit desired purposes. Current research trends have shown that EPS production is dependent on numerous factors which can be combined to varying extent to optimize production yields. Although the majority of research is directed towards their industrial and medicinal uses, these chemical substances possess peculiar characteristics which are also exploited for biomedical research, where they are being used as drug delivery systems, some of which include their abundance in nature, biocompatibility, biodegradability, non-toxicity, and ability to efficiently encapsulate sensitive bioactive agents. However, despite the numerous beneficial prospects of microbial EPSs in drug delivery, there are limitations to the commercial production and industrial applications of these biopolymers. These limitations have inspired revolutionary research into the cost-effective production of safe EPSs polymers. In this review, we classify EPSs and discuss their methods of extraction and characterization. We also summarized current drug delivery applications and discussed limitations to extensive industrial commercialization of EPSs, while highlighting prospects for the utilization of microbial EPSs and implications for research.

Evaluation of extracellular electron transfer in Pseudomonas aeruginosa by co-expression of intermediate genes in NAD synthetase production pathway.

Pseudomonas aeruginosa (PA) is an electrogenic bacterium, in which extracellular electron transfer (EET) is mediated by microbially-produced phenazines, especially pyocyanin. Increasing EET rate in electrogenic bacteria is key for the development of biosensors and bioelectrofermentation processes. In this work, the production of pyocyanin, Nicotinamide Adenine Dinucleotide (NAD) and NAD synthetase by the electrogenic strain PA-A4 is determined using a Microbial Fuel Cell (MFC). Effects of metabolic inhibition and enhancement of pyocyanin and NAD synthetase on NAD/NADH levels and electrogenicity was demonstrated by short chronoamperometry measurements (0-48 h). Combined overexpression of two intermediate NAD synthetase production genes-nicotinic acid mononucleotide adenyltransferase (nadD) and quinolic acid phosphoribosyltransferase (nadC) genes, which are distant on the PA genomic map, enabled co-transcription and increased NAD synthetase activity. The resulting PA-A4 nadD + nadC shows increases in pyocyanin concentration, NAD synthetase activity, NAD/NADH levels, and MFC potential, all significantly higher than its wild type. Extracellular respiratory mechanisms in PA are linked with NAD metabolism, and targeted increased yield of NAD could directly lead to enhanced EET. A previous attempt at enhancing NAD synthetase for electrogenicity by targeting the terminal NAD synthetase gene (nadE) in standard P. aeruginosa PA01 had earlier been reported. Our work however, poses another route to electrogenicity enhancement in PA using; a combination of nadD and nadC. Further experiments are needed to understand specific intracellular mechanisms governing how over-expression of nadD and nadC induced activity of NadE protein. These findings significantly advance the knowledge of the versatility of NAD biosynthetic genes in PA electrogenicity.

Chitinases: expanding the boundaries of knowledge beyond routinized chitin degradation.

Chitinases, enzymes that degrade chitin, have long been studied for their role in various biological processes. They play crucial roles in the moulting process of invertebrates, the digestion of chitinous food, and defense against chitin-bearing pathogens. Additionally, chitinases are involved in physiological functions in crustaceans, such as chitinous food digestion, moulting, and stress response. Moreover, chitinases are universally distributed in organisms from viruses to mammals and have diverse functions including tissue degradation and remodeling, nutrition uptake, pathogen invasion, and immune response regulation. The discovery of these diverse functions expands our understanding of the biological significance and potential applications of chitinases. However, recent research has shown that chitinases possess several other functions beyond just chitin degradation. Their potential as biopesticides, therapeutic agents, and tools for bioremediation underscores their significance in addressing global challenges. More importantly, we noted that they may be applied as bioweapons if ethical regulations regarding production, engineering and application are overlooked.

Production of xylanase by Aspergillus niger GIO and Bacillus megaterium through solid-state fermentation.

Xylanase breaks xylan down to xylose, which is used in industries such as pulp and paper, food and feed, among others. The utilization of wastes for xylanase production is economical, hence this work aimed at producing xylanase through solid-state fermentation and characterizing the enzyme. Xylanase-producing strains of Bacillus megaterium and Aspergillus niger GIO were inoculated separately in a 5 and 10 day solid fermentation study on maize straw, rice straw, sawdust, corn cob, sugarcane bagasse, conifer litters, alkaline-pretreated maize straw (APM) and combined alkaline and biological-pretreated maize straw, respectively. The best substrate was selected for xylanase production. The crude enzyme was extracted from the fermentation medium and xylanase activity was characterized using parameters such as temperature, cations, pH and surfactants. Among different substrates, the highest xylanase activity of 3.18 U ml-1 was recorded when A. niger GIO was grown on APM. The xylanase produced by A. niger GIO and B. megaterium had the highest activities (3.67 U ml-1 and 3.36 U ml-1) at 40 °C after 30 and 45 min of incubation, respectively. Optimal xylanase activities (4.58 and 3.58 U ml-1) of A. niger GIO and B. megaterium , respectively, were observed at pH 5.0 and 6.2. All cations used enhanced xylanase activities except magnesium ion. Sodium dodecyl sulfate supported the highest xylanase activity of 6.13 and 6.90 U ml-1 for A. niger GIO and B. megaterium , respectively. High yields of xylanase were obtained from A. niger GIO and B. megaterium cultivated on APM. The xylanase activities were affected by pH, temperature, surfactants and cations.