Bassam Alkotaini

Biological synthesis of manganese dioxide nanoparticles by Kalopanax pictus plant extract

Manganese dioxide (MnO₂) nanoparticles were synthesised by the reduction of potassium permanganate (KMnO₄) using Kalopanax pictus leaf extract at room temperature. A transparent dark-brown colour appeared after the addition of K. pictus leaf extract to the solution of permanganate. The time course of the reduction of KMnO₄and synthesis of MnO₂ nanoparticles was monitored by means of UV-Vis spectra. The reduction of KMnO₄occurred after addition of plant extract with disappearance of KMnO₄specific peaks and emergence of peak specific for MnO₂nanoparticles. MnO₂nanoparticles showed absorption maxima at 404 nm. The electron dispersive X-ray spectroscopy analyses confirmed the presence of Mn and O in the sample. X-ray photoelectron spectroscopy revealed characteristic binding energies for MnO₂nanoparticles. Transmission electron microscopy micrographs revealed presence of uniformly dispersed spherical shaped particles with average size of 19.2 nm. The selected area electron diffraction patterns revealed the crystalline nature of MnO₂nanoparticles. Fourier transform-infrared spectroscopy spectra of pure MnO₂show the occurrence of O-Mn-O vibrational mode at around 518 cm⁻¹. The phyto-synthesised MnO₂nanoparticles showed degradation ability of dyes (congo red and safranin O) similar to chemically synthesised MnO₂nanoparticles. This study shows simple and eco-friendly synthesis of MnO₂nanoparticles by plant extract and their utilisation for dye degradation for the first time.

Rapid biological synthesis of silver nanoparticles using Kalopanax pictus plant extract and their antimicrobial activity

Silver nanoparticles (AgNPs) have promising potential in biomedicine, energy science, optics, and health care applications. We synthesized AgNPs using plant, Kalopanax pictus leaf extract. UV-visible spectrophotometric study showed the characteristic peak for AgNPs at wavelength 430 nm. The optical density at 430 nm increased after addition of plant leaf extract, indicating increase in formation of nanoparticles. Comparative time course analyses for AgNP synthesis carried out at different reaction temperatures (20, 60, and 90 °C) revealed higher reaction rate for K. pictus than Magnolia kobus plant leaf extract, which showed highest AgNP synthesis rate in the previous report. Electron microscopy analyses confirmed the presence of well dispersed AgNPs, predominantly with spherical shapes. In transmission electron microscopy, the particle size decreased with increase in temperature. Electron dispersive X-ray spectroscopy analyses indicated that Ag content increased with increase in reaction temperature. Fourier transform-infrared spectroscopy studies revealed capping of bioorganics from plant to the synthesized AgNPs. The antimicrobial activity of the synthesized AgNPs against Escherichia coli increased with increase in reaction temperature. The observations in this study will prove beneficial in approaching rapid synthesis of AgNPs and their antimicrobial application.

Production of polyhydroxyalkanoates by batch and fed-batch cultivations of Bacillus megaterium from acid-treated red algae

Polyhydroxyalkanoates (PHAs) are linear polyesters synthesized by microbial fermentation of various substrates. PHAs are accumulated in microbial cells in order to store carbon and energy for future use. We used acid-pre-treated red alga (Gelidium amansii) as a cheap, abundant carbon source to produce PHA via batch and fed-batch cultivation of Bacillus megaterium KCTC 2194. After acid treatment of 10% (w/v) G. amansii, 25.5 g/L galactose, 3.6 g/L glucose, 6 g/L 5-HMF, and 1.05 g/L levulinic acid were formed. In batch culture at pH 7, the dry cell weight (DCW) and PHA content increased to 5.5 g/L and 51.4%, respectively. The cell concentration was enhanced by fed-batch cultivation using two feeding strategies: pH-stat and intermittent feeding. When the pH-stat feeding strategy was employed to add concentrated hydrolysate to the fermentor, DCW increased to 8.2 g/L, with 53.2% PHA content. When concentrated hydrolysate was fed using the intermittent feeding strategy, higher DCW (10.1 g/L) was obtained, along with a slight increase of PHA content to 54.5%. This study demonstrates that red algae could be used after simple acid treatment, to produce PHA without steps for enzymatic hydrolysis and inhibitor removal.

Enhanced catalytic efficiency of endo-β-agarase I by fusion of carbohydrate-binding modules for agar prehydrolysis

Recently, Microbulbifer thermotolerans JAMB-A94 endo-β-agarase I was expressed as catalytic domain (GH16) without a carbohydrate-binding module (CBM). In this study, we successfully constructed different fusions of GH16 with its original CBM6 and CBM13 derived from Catenovulum agarivorans. The optimum temperature and pH for fusions GH16-CBM6, GH16-CBM13, GH16-CBM6-CBM13 and GH16-CBM13-CBM6 were similar to GH16, at 55°C and pH 7. All the constructed fusions significantly enhanced the GH16 affinity (Km) and the catalytic efficiency (Kcat/Km) toward agar. Among them, GH16-CBM6-CBM13 exhibited the highest agarolytic activity, for which Km decreased from 3.67 to 2.11mg/mL and Kcat/Km increased from 98.6 (mg/mL)-1sec-1 to 400.6 (mg/mL)-1sec-1. Moreover, all fusions selectively increased GH16 binding ability to agar, in which the highest binding ability of 95% was obtained with fusion GH16-CBM6-CBM13. Melted agar was prehydrolyzed with GH16-CBM6-CBM13, resulting in a degree of liquefaction of 45.3% and reducing sugar yield of 14.2%. Further addition of Saccharophagus degradans agarolytic enzymes resulted in mono-sugar yields of 35.4% for galactose and 31.5% for 3,6-anhydro-l-galactose. There was no pH neutralization step required and no 5-hydroxymethylfurfural detected, suggesting the potential of a new enzymatic prehydrolysis process for efficient production of bio-products such as biofuels.

Potential of biosynthesized silver nanoparticles as nanocatalyst for enhanced degradation of cellulose by cellulase

Silver nanoparticles (AgNPs) as a result of their excellent optical and electronic properties are promising catalytic materials for various applications. In this study, we demonstrate a novel approach for enhanced degradation of cellulose using biosynthesized AgNPs in an enzyme catalyzed reaction of cellulose hydrolysis by cellulase. AgNPs were synthesized through reduction of silver nitrate by extracts of five medicinal plants (Mentha arvensis var. piperascens, Buddleja officinalisMaximowicz, Epimedium koreanum Nakai, Artemisia messer-schmidtiana Besser, and Magnolia kobus). An increase of around twofold in reducing sugar formation confirmed the catalytic activity of AgNPs as nanocatalyst. The present study suggests that immobilization of the enzyme onto the surface of the AgNPs can be useful strategy for enhanced degradation of cellulose, which can be utilized for diverse industrial applications.

Potential of Bacillus megaterium for production of polyhydroxyalkanoates using the red algae Gelidium amansii

To investigate the ability to accumulate polyhydroxyalkanoates (PHA) using either acid-treated or un-treated red algae (Gelidium amansii) as a carbon source, a total of six Bacillus megaterium strains were tested. All strains were able to grow considerably when acid-treated algae were used, where strain KCTC 3712 reached highest total dry cell weight (DCW) of 4.1 g/L with a PHA content of 30%. Strain KCTC 2194 accumulated highest PHA of 55% with a total DCW of 3.3 g/L from treated algae. By using un-treated G. amansii as a carbon source, weak growth was observed in all strains. Strains KCTC 1366 and KCTC 3007 reached DCWs of 2.0 and 1.2 g/L and PHA contents of 23 and 27%, respectively, from un-treated algae. This is the first report on PHA production from acidtreated and un-treated red algae.

Fusion of agarase and neoagarobiose hydrolase for mono-sugar production from agar

In enzymatic saccharification of agar, endo- and exo-agarases together with neoagarobiose hydrolase (NABH) are important key enzymes for the sequential hydrolysis reactions. In this study, a bifunctional endo/exo-agarase was fused with NABH for production of mono-sugars (d-galactose and 3,6-anhydro-l-galactose) from agar using only one fusion enzyme. Two fusion enzymes with either bifunctional agarase (Sco3476) or NABH (Zg4663) at the N-terminus, Sco3476–Zg4663 (SZ) and Zg4663–Sco3476 (ZS), were constructed. Both fusion enzymes exhibited their optimal agarase and NABH activities at 40 and 35xa0°C, respectively. Fusions SZ and ZS enhanced the thermostability of the NABH activity, while only fusion SZ showed a slight enhancement in the NABH catalytic efficiency (Kcat/KM) from 14.8 (mg/mL)−1xa0s−1 to 15.8 (mg/mL)−1xa0s−1. Saccharification of agar using fusion SZ resulted in 2-fold higher mono-sugar production and 3-fold lower neoagarobiose accumulation when compared to the physical mixture of Sco3476 and Zg4663. Therefore, this fusion has the potential to reduce enzyme production cost, decrease intermediate accumulation, and increase mono-sugar yield in agar saccharification.

Fusion of Carbohydrate Binding Modules to Bifunctional Cellulase to Enhance Binding Affinity and Cellulolytic Activity

Bifunctional cellulase (glycoside hydrolase 5, GH5) from Bacillus sp. D04 having both endo- and exoglucanase activities was fused with two types of carbohydrate binding modules (CBMs). CBM3 from Bacillus sp. D04 and CBM9 from Thermotoga maritima Xyn10A were added to GH5 to hydrolyze microcrystalline cellulose (Avicel) as well as water-soluble cellulose (carboxymethyl cellulose, CMC). The optimum temperature of GH5 was 50oC, while it increased to 60oC for the fusion GH5-CBM3 and GH5-CBM9, indicating that addition of CBM increased the thermostability of the enzyme. Addition of CBM3 and CBM9 enhanced the GH5 affinity (KM), for which KM decreased from 104 to 33.9 ~ 35.1 mg/mL for CMC, and from 115 to 55.5 ~ 80.3 mg/mL for Avicel, respectively. The catalytic efficiency (kcat/KM) also increased from 4.80 to 5.36 ~ 6.46 (mL/mg)/sec for CMC, and from 1.77 to 2.40 ~ 4.45 (mL/mg)/sec for Avicel, respectively, by addition of CBM3 and CBM9.