Diapolycopenedioic-acid-diglucosyl ester and keto-myxocoxanthin glucoside ester: Novel carotenoids derived from Exiguobacterium acetylicum S01 and evaluation of their anticancer and anti-inflammatory activities

Inflammation is pivotal for the development of gastrointestinal cancer and linked to poor survival and limited therapeutic options. In this study, six structurally different carotenoids were isolated and identified from the methanolic extract of Exiguobacterium acetylicum S01 namely lycopene (Car-I), diapolycopenedioic-acid-diglucosyl-ester (Car-II), β-carotene (Car-III), zeaxanthin (Car-IV), astaxanthin (Car-V), and keto-myxocoxanthin glucoside-ester (Car-VI). Further, their anti-cancer, anti-inflammatory, and antioxidant potentials were evaluated. The MTT assay was used to determine the effect of carotenoids on viability of colorectal cancer (HT-29) as well as peripheral blood mononuclear cells (PBMCs). Results revealed that all the six carotenoids were demonstrated a significant inhibition of HT-29 cells viability in a dose-dependent manner whereas there was no cytotoxic effect in PBMCs. The study also recorded that six carotenoids considerably inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production, tumor necrosis factor-alpha (TNF-α), and lipid peroxidation in PBMCs. Moreover, antioxidant potentials of Car-II and Car-VI were significantly (p = 0.001) higher than ascorbic acid as determined by a 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay. Therefore, our results ascertained the role of carotenoids derived from E. acetylicum S01 in developing potential therapeutic agents for inflammation-associated cancer.

β-Galactosidase from Exiguobacterium acetylicum: Cloning, expression, purification and characterization

The main goal of this work was to evaluate the performance of β-galactosidase from Exiguobacterium acetylicum MF03 in both hydrolysis and transgalactosylation reactions from different substrates. The enzyme gene was expressed in Escherichia coli BL21 (DE3), sequenced, and subjected to bioinformatic and kinetic assessment. Results showed that the enzyme was able to hydrolyze lactulose and o-nitrophenyl-β-d-galactopyranoside, but unable to hydrolyze lactose, o-nitrophenyl-β-d-glucopyranoside, butyl- and pentyl-β-d-galactosides. This unique and novel substrate specificity converts the E. acetylicum MF03 β-galactosidase into an ideal catalyst for the formulation of an enzymatic kit for lactulose quantification in thermally processed milk. This is because costly steps to eliminate glucose (resulting from hydrolysis of lactose when a customary β-galactosidase is used) can be avoided.

Growth promotion of wheat seedlings by Exiguobacterium acetylicum 1P (MTCC 8707) a cold tolerant bacterial strain from the Uttarakhand Himalayas

Exiguobacterium acetylicum strain 1P (MTCC 8707) is a gram-positive, rod-shaped, yellow pigmented bacterium isolated from soil on nutrient agar plates at 4°C. The identity of the bacterium was arrived on the basis of the biochemical characterization, BIOLOG sugar utilization pattern and sequencing of the 16S rRNA gene. It grew at temperatures ranging from 4 to 42°C, with temperature optima at 30°C. It expressed multiple plant growth promotion attributes such as phosphate solubilization, indole acetic acid (IAA), siderophore and hydrogen cyanide (HCN) production, differentially at suboptimal growth temperatures (15 and 4°C). At 15°C it solubilized phosphate (21.1 μg of P ml(-1) day(-1)), and produced IAA (14.9 μg ml(-1) day(-1)) in tryptophan amended media. Qualitative detection of siderophore production and HCN were possible at 15°C. At 4°C it retained all the plant growth promotion attributes. Seed bacterization with the isolate, positively influenced the growth and nutrient uptake parameters of wheat seedlings in glass house studies at suboptimal cold growing temperatures.