Antoine F. Mulaba-Bafubiandi

Development and Characterization of Curcumin Loaded Silver Nanoparticle Hydrogels for Antibacterial and Drug Delivery Applications

The present work involves the development of curcumin loaded silver hydrogel nanocomposites based on acrylamide and 2-acrylamido-2-methyl propanesulfonic acid, as a template by redox co-polymerization in the presence of hydrophilic crosslinker N,N1-methylenebisacrylamide. Silver nitrate was taken as the metal precursor and sodium borohydride as a reducing agent. The formation of silver nanoparticles was monitored using UV–Vis absorption spectroscopy. The developed hydrogel silver nanocomposites (HSNC) were characterized by FTIR, UV–Vis, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. The curcumin loading and release characteristics were performed for different hydrogel systems. The developed HSNCs were evaluated for preliminary antibacterial applications.

Synthesis of Surfactant-Modified Poly (Acrylamide-co-Potassium Acrylate) Hydrogels and Its in vitro Release Studies

In present investigation, a series of hydrogels, composed with Surfactant and poly(Acrylamide-co-Potassium acrylate), using Ammonium per sulfate(APS)/N,N,N 1 , N 1 -tetram ethylethylene diamine (TMEDA) initiating system and N,N 1-methylenebisacrlyamide (MBA) as crosslinker. The prepared hydrogel was characterized by using Fourier transform infrared spectroscopy (FTIR), Thermo gravimetric analysis (TGA), Scanning electron microscopy (SEM). The controlled release characteristics of the matrices for Triprolidene hydrochloride (TH) were investigated in pH 7.4 media. Drug was released in a controlled manner up to 1400 min.

Microbes Assisted Mineral Flotation a Future Prospective for Mineral Processing Industries: A Review

ABSTRACT The latest advancements in mineral biotechnology developed environmental benign microbial flotation processes for mineral beneficiation. Several studies were conducted to evaluate the microbes and microbial metabolites as flotation reagents for separation of gangue materials from valuable minerals. The available scientific literatures on microbial flotation process suggest that, interactions of minerals with cells of certain bacteria and microbial metabolites have a significant effect on their surface properties. As a consequence, bacterial cells belong to genera Acidithiobacillus, Leptospirillum, Mycobacterium, Staphylococcus, and Bacillus, etc., and microbial metabolites such as bio-surfactants, extracellular polymeric substances (EPS) and nucleic acid have been used as collectors and surface modifiers in the mineral flotation process. The characteristic properties of the microbial surfactants such as their abilities to lower surface tensions and foaming capacity prompted their application as frother in mineral flotation process. To date, microbial flotations have primarily studied in laboratory scale; however, there is ample scope to expand this eco-friendly process for mineral processing industries. The current review addresses the recent developments and applications of microorganisms and bio-molecules in mineral flotation processes.

Performance enhancement of the poly (vinyl alcohol) (PVA) by activated natural clay clinoptilolite for pervaporation separation of aqueous–organic mixtures

AbstractThe pervaporation (PV) performance of poly (vinyl alcohol) (PVA) is enhanced by the addition of natural clay clinoptilolite into it. Nanocomposites of glutaraldehyde cross-linked (in situ) PVA/clinoptilolite membranes were prepared by solution casting technique to investigate the water flux, selectivity, perm selectivity and enrichment factor. PV experiments using clay incorporated membrane matrix (CIMM) have been performed at 30, 40 and 50°C to separate water–isopropanol/ethanol feed mixtures containing 10–40 wt. % of water. These membranes were characterized by universal testing machine to understand the mechanical strength. The morphological analysis has been studied using scanning electron microscopy. The high content (5 and 10%) of clay in the CIMM extracts water efficiently on the permeate side with high selectivity. The hydrophilic nature of clay and the formation of CIMM are responsible to offer such increased separation of water over the organic components of the feed mixtures.

Advances in microbial leaching processes for nickel extraction from lateritic minerals - A review

Lateritic nickel minerals constitute about 80% of nickel reserves in the world, but their contribution for nickel production is about 40%. The obstacles in extraction of nickel from lateritic minerals are attributed to their very complex mineralogy and low nickel content. Hence, the existing metallurgical techniques are not techno-economically feasible and environmentally sustainable for processing of such complex deposits. At this juncture, microbial mineral processing could be a benevolent approach for processing of lateritic minerals in favor of nickel extraction. The microbial mineral processing route offers many advantages over conventional metallurgical methods as the process is operated under ambient conditions and requires low energy input; thus these processes are relatively simple and environment friendly. Microbial processing of the lateritic deposits still needs improvement to make it industrially viable. Microorganisms play the pivotal role in mineral bio-processing as they catalyze the extraction of metals from minerals. So it is inevitable to explore the physiological and bio-molecular mechanisms involved in this microbe-mineral interaction. The present article offers comprehensive information about the advances in microbial processes for extraction of nickel from laterites.

Studies on Curcumin Loaded Poly(N-isopropylacrylamide) Silver Nanocomposite Hydrogels for Antibacterial and Drug Releasing Applications

Design of silver nanoparticles containing poly(N-isopropylarclamide) (PNIPAAm) hydrogels were prepared by free-radical polymerization of N-isopropylarclamide as an environmentally sensitive monomer and MBA as a crosslinker in an aqueous medium. The embedded silver nanocomposite hydrogels (AgNCH) structure were characterized by, UV-Vis, FTIR, DLS, TEM and X-ray analysis. Curcumin loading and release characteristics were performed for PNIPAAm hydrogel, silver ions loaded hydrogels as well as silver nanocomposite hydrogels. These curcumin loaded silver nanocomposite hydrogels exhibit excellent antibacterial action on Escherichia coli (E. coli). Therefore, the present study clearly provides novel antimicrobial hydrogels which are potentially useful in biomedical applications.

Optimization of Process Variables for the Biosynthesis of Silver Nanoparticles by Aspergillus wentii using Statistical Experimental Design

The present scientific endeavour focuses on the optimization of process parameters using central composite design towards development of an efficient technique for the biosynthesis of silver nanoparticles. The combined effects of three process variables (days of fermentation, duration of incubation, concentration of AgNO3) upon extracellular biological synthesis of silver nanoparticles (AgNPs) by Aspergillus wentii NCIM 667 were studied. A single absorption peak at 455 nm confirming the presence of silver nanoparticles was observed in the UV-visible spectrophotometric graph. Using Fourier transform infrared spectroscopic analysis the presence of proteins as viable reducing agents for the formation AgNPs was recorded. High resolution transmission electron microscopy showed the realization of spherically shaped AgNPs of size 15–40 nm. Biologically formed AgNPs revealed higher antimicrobial activity against gram-negative than gram-positive bacterial strains. We present the enumeration of the properties of biosynthesized nanoparticles which exhibit photocatalysis exhausting an organic dye, the methyl orange, upon exposure to sunlight thereby accomplishing the degradation of almost (88%) the methyl orange dye within 5 h.

Optimization of Microbial Leaching of Base Metals from a South African Sulfidic Nickel Ore Concentrate by Acidithiobacillus ferrooxidans

ABSTRACT X-ray diffraction analysis revealed that pentlandite and chalcopyrite were the prominent mineral phases in a South African sulfidic nickel ore concentrate that hosted nickel and copper. Cobalt was found to be closely associated with the nickel-bearing pentlandite phase of the ore sample. Microbial batch leaching experiments designed according to a central composite design model were run for 15 days in a shaking incubator (150 rpm) at a constant temperature (30°C) with variations in experimental parameters like ore pulp density, particle size, bacterial inoculum, pH of the culture medium, and residence time. Quadratic mathematical models were developed to predict the rate of metal extractions. The suitability of the model of the microbial leaching process was confirmed from normal probability curves. An analysis of variance indicated that the residence time, pulp density of the ore, and particle size were the most significant factors. Bacterial inoculum size hardly showed any effect on the total metal extractions. Maximum nickel (82%), cobalt (76%) and copper (25.6%) extractions were achieved under optimum conditions, operated for 15 days at pulp density of 2% and particle size of −75 µm at pH 1.5.

Bioprocessing of jackfruit (Artocarpus heterophyllus L.) pulp into wine: Technology, proximate composition and sensory evaluation

Major wineries are confined to using grapes as substrate, as a result of which other fruits, especially in the tropical zone, remain underutilised. A wine, from jackfruit (Artocarpus heterophyllus L.) pulp, was prepared by fermenting with wine yeast (Saccharomyces cerevisiae) as starter culture. The wine had the following proximate compositions: total soluble solids, 1.8° Brix; total sugar, 4.32 g/100 ml; titratable acidity, 1.16 g tartaric acid/ 100 ml; pH, 3.52; total phenolics, 0.78 g/100 ml; β-carotene, 12 µg/100 ml; ascorbic acid, 1.78 g/100 ml; lactic acid, 0.64 mg/100 ml and ethanol content of 8.23% (v/v). The jackfruit wine had a DPPH scavenging activity of 32% at a dose of 250 µg/ml. The jackfruit wine was well accepted among consumers as per its organoleptic properties. Principal component analysis reduced the 10 original analytical and proximate variables (TSS, total sugar, TA, pH, phenol, β-carotene, ascorbic acid, lactic acid, ethanol and DPPH scavenging activity) into four independent components which accounted for 83.42% of variations.

Clayey minerals and clayey soils as possible microorganism repositories

Clay minerals are one of the most abundant and crucial structural materials of the Earth’s crust, playing a significant role in many aspects of life. The present study aims to critically investigate the presence of microorganisms within different clayey soil samples. Microorganisms are ubiquitous by nature due to their natural ability to adapt to different habitats. Bacteria and Archea are the most abundant microorganisms in the soil and serve many important roles like nitrogen fixation. Fungi are also an integral part of the soil micro flora as they serve as food sources to other organisms as well as facilitate as layer organisms with beneficial relationships to plants. The continued evolution of man and subsequent use of clayey soils in areas such as pottery, cosmetics, engineering and geophagia brings into question whether microorganisms are harmful. Soil samples with high amounts of fine particles and colloidal substances were studied while taking into account the identified hydrated aluminosilicates and their roles in bioavailability. The study also investigated the possible types of microbial flora associated with each type of clayey soil as well as their functions within the human body. Considering the diverse origin of these microorganisms, we discuss their modes of attachment to clayey soils with the aim of minimising their transmission to humans.