Fariha Hasan

Biological degradation of plastics: a comprehensive review.

Lack of degradability and the closing of landfill sites as well as growing water and land pollution problems have led to concern about plastics. With the excessive use of plastics and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. Awareness of the waste problem and its impact on the environment has awakened new interest in the area of degradable polymers. The interest in environmental issues is growing and there are increasing demands to develop material which do not burden the environment significantly. Biodegradation is necessary for water-soluble or water-immiscible polymers because they eventually enter streams which can neither be recycled nor incinerated. It is important to consider the microbial degradation of natural and synthetic polymers in order to understand what is necessary for biodegradation and the mechanisms involved. This requires understanding of the interactions between materials and microorganisms and the biochemical changes involved. Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. This paper reviews the current research on the biodegradation of biodegradable and also the conventional synthetic plastics and also use of various techniques for the analysis of degradation in vitro.

Methods for detection and characterization of lipases: A comprehensive review.

Microbial lipases are very prominent biocatalysts because of their ability to catalyze a wide variety of reactions in aqueous and non-aqueous media. The chemo-, regio- and enantio-specific behaviour of these enzymes has caused tremendous interest among scientists and industrialists. Lipases from a large number of bacterial, fungal and a few plant and animal sources have been purified to homogeneity. This article presents a critical review of different strategies which have been employed for the detection, purification and characterization of microbial lipases.

Aminoglycoside resistance of Pseudomonas aeruginosa biofilms modulated by extracellular polysaccharide

Pseudomonas aeruginosa is an opportunistic pathogen that produces sessile communities known as biofilms that are highly resistant to antibiotic treatment. Limited information is available on the exact role of various components of the matrix in biofilm-associated antibiotic resistance. Here we show that the presence of extracellular polysaccharide reduced the extent of biofilm-associated antibiotic resistance for one class of antibiotics. Minimal bactericidal concentration (MBC) for planktonic and biofilm cells of P. aeruginosa PA14 was measured using a 96 well microtiter plate assay. The MBC of biofilm-grown ΔpelA mutant, which does not produce the Pel polysaccharide, was 4-fold higher for tobramycin and gentamicin, and unchanged for ΔbifA mutant, which overproduces Pel, when compared to the wild type. Biofilms of pelA mutants in two clinical isolates of P. aeruginosa showed 4- and 8-fold higher MBC for tobramycin as compared to wild type. There was no difference in the biofilm resistance of any of these strains when tested with fluoroquinolones. This work forms a basis for future studies revealing the mechanisms of biofilm-associated antibiotic resistance to aminoglycoside antibiotics by P. aeruginosa.

Extended-Spectrum β-Lactamases (ESBLs): Characterization, Epidemiology and Detection

β-lactamases of Enterobacteriaceae are the most important mechanism of resistance against β-lactam drugs. Two types of β-lactamases can confer resistance against 3rd generation cephalosporins. Chromosomally mediated β-lactamases are inducible and are not inhibited by clavulanic acid. Resistance due to these enzymes is non-transferable. The 2nd type of enzyme is plasmid-mediated β-lactamases, which are inhibited by clavulanic acid. These enzymes are more important clinically as these can be transferred between various species of Enterobacteria ceae. These enzymes are called extended-spectrum β-lactamases (ESBLs). ESBL-producing Enterobacteriaceae have been responsible for numerous outbreaks of infection throughout the world and pose challenging infection control issues. Antibacterial choice is often complicated by multi-resistance. ESBLs can confer resistance against all β-lactam drugs except carbapenems and cephamycins. Nursing home patients may be an important reservoir of ESBL-containing multiple antibiotic-resistant organisms. Use of broad-spectrum oral antibiotics and probably poor infection control practices may facilitate spread of this plasmid-mediated resistance. In addition to known populations at risk, ambulatory patients with chronic conditions represent another patient population that may harbor ESBL-producing organisms. Various methods can be used for detection of ESBLs in the laboratory. These tests include double disc diffusion test, Vitek ESBL test, E Tests, MIC Determination, genetic method, and isoelectric focusing (IEF).

Encapsulation of Ellipticine in poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) based nanoparticles and its in vitro application.

Biodegradable, biocompatible, renewable and non-toxic polyhydroxyalkanoates (PHAs) based nanoparticles are the novel nanotherapeutic tool which are used for the encapsulation of antineoplastic drugs for cancer therapy. In this study, poly-3-hydroxybutyrate-co-5 mol% 3-hydroxyvalerate (PHBV-S), poly-3-hydroxybutyrate-co-11 mol% 3-hydroxyvalerate (PHBV-11) and poly-3-hydroxybutyrate-co-15 mol% 3-hydroxyvalerate (PHBV-15) were used as a nanocarrier for encapsulation of Ellipticine (EPT). EPT is a model anticancer drug. Physicochemical characteristics such as particle size, its morphology and zeta potential of blank and EPT loaded PHBV-S, PHBV-11 and PHBV-15 nanoparticles were studied. In vitro cytotoxicity tests confirmed that the blank PHBV-S, PHBV-11 and PHBV-15 nanoparticles were demonstrating significant biocompatibility without affecting the survival of cancer cell line A549. The loading efficiency of EPT in PHBV nanoparticles was observed in the range of 39.32 to 45.65%. The % inhibition of cancer cell line A549 ranged from 64.28 to 67.77% in comparison to EPT alone in which % inhibition found to be ≤45.11%. The IC50 value for each of three different formulations of EPT loaded PHBV nanoparticles ranged from 1.00 to 1.31 μg/mL. The order of % inhibition of cancer cell line A549 for drug loaded nanoparticles was EPT-PHBV-15>EPT-PHBV-S>EPT-PHBV-11. This system had demonstrated a great potential to increase the cytotoxic effect of EPT by increasing its bioavailability.

Degradation of polyurethane by novel bacterial consortium isolated from soil

The present study describes the isolation of bacteria from soil with the ability to degrade plastic polyurethane (PU). Bacterial strains attached on the polyurethane film, after soil burial for 6 months, were isolated and identified asBacillus sp. AF8,Pseudomonas sp AF9,Micrococcus sp. 10,Arthrobacter sp. AF11, andCorynebacterium sp. AF12. In plate assay, zones of hydrolysis were visualised around the bacterial colonies on mineral salt agar plates containing polyurethane as a sole carbon source. The results of the Sturm test for degradability showed more CO2 production in the test than in control. The production of esterase was detected in the presence of polyurethane as a substrate. The Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy showed certain changes on the surface of PU film and formation of some new intermediate products after polymer breakdown.

Degradation of polyester polyurethane by a newly isolated soil bacterium, Bacillus subtilis strain MZA-75

A polyurethane (PU) degrading bacterial strain MZA-75 was isolated from soil through enrichment technique. The bacterium was identified through 16S rRNA gene sequencing, the phylogenetic analysis indicated the strain MZA-75 belonged to genus Bacillus having maximum similarity with Bacillus subtilis strain JBE0016. The degradation of PU films by strain MZA-75 in mineral salt medium (MSM) was analyzed by scanning electron microscopy (SEM), fourier transform infra-red spectroscopy (FT-IR) and gel permeation chromatography (GPC). SEM revealed the appearance of widespread cracks on the surface. FTIR spectrum showed decrease in ester functional group. Increase in polydispersity index was observed in GPC, which indicates chain scission as a result of microbial treatment. CO2 evolution and cell growth increased when PU was used as carbon source in MSM in Sturm test. Increase in both cell associated and extracellular esterases was observed in the presence of PU indicated by p-Nitrophenyl acetate (pNPA) hydrolysis assay. Analysis of cell free supernatant by gas chromatography–mass spectrometry (GC–MS) revealed that 1,4-butanediol and adipic acid monomers were produced. Bacillus subtilis strain MZA-75 can degrade the soft segment of polyester polyurethane, unfortunately no information about the fate of hard segment could be obtained. Growth of strain MZA-75 in the presence of these metabolites indicated mineralization of ester hydrolysis products into CO2 and H2O.

Influence of culture conditions on lipase production byBacillus sp. FH5

Lipases are a class of enzymes, which catalyse the hydrolysis of long chain triglycerides. Microbial lipases are currently receiving much attention with the rapid development of enzyme technology. Lipases have industrial potential in the chemical, pharmaceutical, medical, cosmetic, leather and paper manufacturing industries, biosurfactant synthesis, and agrochemicals. ABacillus strain isolated from soil was tested for the production of extracellular lipase, by batch culturing in shake flask. The growth conditions were optimised for the maximum production of enzyme. Various parameters for the production of lipase, such as temperature, incubation period, pH, carbon source, nitrogen source and lipids were studied. Maximum lipase production was found in 48-h-old culture filtrate at 37 °C, pH 8.0. Among all the carbon sources, salicin gave the maximum activity and among all the nitrogen sources yeast extract gave maximum production/activity. Tween (20 and 80) does not stimulate the growth much but assisted in enzyme production.

Importance of Proteins Controlling Initiation of DNA Replication in the Growth of the High-Pressure-Loving Bacterium Photobacterium profundum SS9

The molecular mechanism(s) by which deep-sea bacteria grow optimally under high hydrostatic pressure at low temperatures is poorly understood. To gain further insight into the mechanism(s), a previous study screened transposon mutant libraries of the deep-sea bacterium Photobacterium profundum SS9 and identified mutants which exhibited alterations in growth at high pressure relative to that of the parent strain. Two of these mutants, FL23 (PBPRA3229::mini-Tn10) and FL28 (PBPRA1039::mini-Tn10), were found to have high-pressure sensitivity and enhanced-growth phenotypes, respectively. The PBPRA3229 and PBPRA1039 genes encode proteins which are highly similar to Escherichia coli DiaA, a positive regulator, and SeqA, a negative regulator, respectively, of the initiation of DNA replication. In this study, we investigated the hypothesis that PBPRA3229 and PBPRA1039 encode DiaA and SeqA homologs, respectively. Consistent with this, we determined that the plasmid-carried PBPRA3229 and PBPRA1039 genes restored synchrony to the initiation of DNA replication in E. coli mutants lacking DiaA and SeqA, respectively. Additionally, PBPRA3229 restored the cold sensitivity phenotype of an E. coli dnaA(Cs) diaA double mutant whereas PBPRA1039 suppressed the cold sensitivity phenotype of an E. coli dnaA(Cs) single mutant. Taken together, these findings show that the genes disrupted in FL23 and FL28 encode DiaA and SeqA homologs, respectively. Consequently, our findings add support to a model whereby high pressure affects the initiation of DNA replication in P. profundum SS9 and either the presence of a positive regulator (DiaA) or the removal of a negative regulator (SeqA) promotes growth under these conditions.

Psychrophilic and psychrotrophic fungi: a comprehensive review

This article reviews the comparative diversity of psychrophilic and psychrotrophic fungi, their adaptability mechanisms for survival and potential applications in biotechnology and pharmaceuticals. Fungi are able to grow and survive at low temperature and exist widely in polar and non-polar habitats. These cold regions are known for very low temperature, high ultra violet-B radiation, frequent freeze and thaw cycles and low water and nutrient availability. Most of the fungi adapt to such harsh conditions by evolving various strategies in their metabolism and physiology. Psychrophilic and psychrotrophic fungi are of importance in biotechnological and pharmaceutical fields due to their diverse characteristics developed or evolved due to their adaptation and survival in extreme environments, like; production of cold-active enzymes, pharmaceutical or bioactive metabolites and exo-polysaccharides, have potential for bioremediation and can also be used as biofertilizer.