Production and Purification of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Degrading Enzyme from Streptomyces sp. AF-111

A poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) degrading bacterial strain designated as AF-111 was isolated from sewage sludge sample. The bacterium was identified by 16S rRNA gene sequencing. The results revealed that strain AF-111 showed 99 % similarity with Streptomyces althioticus strain NRRL B-3981 and designated as Streptomyces sp. strain AF-111. An extracellular PHBV depolymerase enzyme was produced under optimized conditions and purified through ammonium sulphate fractionation and column chromatography. The enzyme was purified to homogeneity, indicated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and molecular weight was found to be approximately 51 kDa. Effect of temperature, pH, metal ions and inhibitors on the PHBV depolymerase activity was determined. The enzyme was stable at wide range of temperature (35–55 °C) and pH (6–8). PHBV depolymerase was stable in the presence of different metal ions except iron and zinc which had inhibitory effect on depolymerase activity. Both ethylenediamine teteracetic acid and phenylmethyl sulphonyl fluoride strongly inhibited enzyme activity which indicates that this enzyme belongs to the serine hydrolase family like other polyhydroxyalkanoate depolymerases. The results show that a depolymerase from strain AF-111 can effectively degrade PHBV, therefore, it can be applied in the process of biochemical monomer recycling.     

Enhancement of biomethane production from cattle manure with codigestion of dilute acid pretreated lignocellulosic biomass

It is well known that dilute sulfuric acid pretreatment of the lignicellulosisc biomass is an effective approach used for the production of the ethanol. However, there are less studies on the biogas production from the pretreated lignocellulosics and hardly data available on the codigestion of cattle manure with the pretreated lignocellulosisc material. The aim of this study was to evaluate biomethane production potential of codigestion of cattle manure with dilute acid pretreated lignocellulosic biomass. Sugarcane bagasse and rice husk was pretreated with dilute sulfuric acid or phosphoric acid at 121°C for 20 minutes and subsequently subjected to anaerobic digestion alone or codigested with cattle manure.

The results showed that codigestion of 1% phosphoric acid pretreated rice husk with cattle manure led to the highest methane production of 115 Nmlg^?1VS while monodigestion of cattle manure and phosphoric acid pretreated rice husk produced 98 and 87 Nmlg^?1VS, respectively. An inhibition was observed in anaerobic digestion of sulfuric acid pretreated rice husk and sugarcane bagasse during monodigestion and codigestion with cattle manure.

The study concludes that dilute phosphoric acid pretreated lignocellulosics like sugarcane bagasse and rice husk can be used as a cosubstrate with cattle manure in anaerobic digestion for enhanced methane production. Dilute sulfuric acid pretreatment, which is effective method for the bioethanol production, causes inhibition during anaerobic digestion of the pretreated lignocellulosics.     

Biosynthesis and Characterization of Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) from Bacillus cereus S10

The biodegradable and biocompatible copolymer poly-(3-hydroxybutyrate-co-5 mol% 3-hydroxyvalerate), poly-(3HB-co-5 mol% 3HV), was synthesized by Bacillus cereus S10 and the highest yield was determined as 69.91 % at pH 7 and 30 °C after 48 h of incubation using a glucose as the sole carbon source. Poly-(3HB-co-5 mol% 3HV) was purified from bacterial biomass using chloroform. FTIR analysis showed absorption bands at 1,723, 1,274, 1,373, 1,453, 2,932 cm^?1 corresponding to C=O, C–O stretching, CH₃, –CH₂ and –CH groups, respectively. ¹H-NMR and ¹³C-NMR analysis confirmed that the copolymer was composed of 95 mol% of 3-hydroxybutrate and 5 mol% of 3-HV monomeric units. Poly-(3-HB-co-5 mol% 3HV) was used for nanoparticles preparation. The diameter of nanoparticles was 202 nm.     

Simple graphical method for inherent occupational health assessment

The concept of inherently safer design was introduced to design a fundamentally safer process so that hazards can be avoided or minimized rather than controlled or managed. The ideology has later been extended to the environmental, but not health criteria due to its complicated underlying principles. Even though health risk methods are already established, majority are for existing plants assessment. Early consideration of health aspect starting from process design stage however, has received much less attention. This paper introduces a simple graphical method to evaluate the inherent occupational health hazards of chemical processes during the R&D stage. A survey was conducted to identify the important health parameters for the graphical method development, involving nine world inherent safety and health experts. Based on their input, process mode, material volatility, operating pressure and chemical health hazard (toxicity and adverse effect) are the significant factors affecting inherent health hazards of chemical processes. The choice of parameters was bounded by the information availability at this stage. The method was applied on six routes to methyl methacrylate and ten routes to acetic acid. The parameters were plotted for each subprocess of the alternative routes. The ‘healthiest’ route was selected based on thorough hazards assessment across all the subprocesses. The first case study reveals the tertiary butyl alcohol as the ‘healthiest’ one as it poses relatively lower, or at least comparable hazards to the other routes due to exposure and health impacts. Meanwhile the acetic acid case study indicates ethanol oxide and ethyl oxide based routes as the inherently healthier as they operate at lower operating pressure besides posing comparable hazards level for the other three parameters, compared to the other routes. The case studies show that the inherent occupational health of a chemical process can already be evaluated easily in the R&D stage with the simple graphical method proposed.     

Biosurfactants and chemotaxis interplay in microbial consortium-based hydrocarbons degradation

Environmental Science and Pollution Research - Hydrocarbons are routinely detected at low concentrations, despite the degrading metabolic potential of ubiquitous microorganisms. The potential...