Biohydrogen production by a novel thermotolerant photosynthetic bacterium Rhodopseudomonas pentothenatexigens strain KKU-SN1/1

Thirty-nine purple non-sulfur bacteria (PNSB) were isolated from 162 environmental samples. These isolates of PNSB were tested for their ability to produce biohydrogen (Bio-H₂) at 40 °C and only 14 isolates were noted to possess such ability, which were considered as thermotolerant photosynthetic Bio-H₂ producing bacteria (tt-PHPB). Of 14 isolates of tt-PHPB, KKU-SN1/1 was observed to have the highest Bio-H₂ productivity. Central composite design was employed to optimize the operating conditions for maximal Bio-H₂ production by the strain KKU-SN1/1. Under optimal conditions (7.6 g/L malic acid, 11 g/L glutamic acid, pH 6.7, at 40 °C) the Bio-H₂ production was increased by 68.28%. The purity of Bio-H₂ produced was 92.22%, as suggested by gas chromatography (GC-TCD). Based on morphological characteristics and 16S rDNA sequence analysis, the strain KKU-SN1/1 was identified as Rhodopseudomonas pentothenatexigens, with 99.7% similarity. To our knowledge, this is the first report on Bio-H₂ production by R. pentothenatexigens KKU-SN1/1.     

The Improvement in Mechanical and Barrier Properties of Poly(Vinyl Alcohol)/Graphene Oxide Packaging Films

In this study, poly(vinyl alcohol) (PVA)‐graphite oxide and PVA‐graphene oxide (XGO) films were prepared by simple and environmentally friendly method. Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscope revealed the strong hydrogen‐bonding interactions between XGO and PVA matrix and the layered structure of tensile fracture surfaces of exfoliated PVA‐XGO films. These resulted in a remarkable improvement on mechanical and barrier properties of XGO/PVA nanocomposite films. The addition of 0.3 and 2.0 wt.% XGO showed an increase in tensile strength (49%) and failure stain (13–22%), in comparison with the neat PVA films. The dramatic improvement of 144% in elastic modulus was observed in PVA/2.0 wt.% XGO. Both O₂ and water vapour permeability coefficients of PVA film decreased by about 76% and 21% at an XGO loading of 2.0 wt.%, respectively. Preliminary test was performed to determine the use of nanocomposite films to extend the shelf life of bananas. It was found that bananas packaged in nanocomposite films were ripened slower than those unpackaged or packaged in PVA films. These results demonstrate that such films could dramatically promote the application of PVA‐based films in the packaging industry. Copyright © 2015 John Wiley & Sons, Ltd.     

Broad distribution of enterotoxin genes (hblCDA, nheABC, cytK, and entFM) among Bacillus thuringiensis and Bacillus cereus as shown by novel primers

Eight new pairs of PCR primers were designed and efficiently detect eight toxin genes (hblC, hblD, hblA, nheA, nheB, nheC, cytK, and entFM) in 411 B. cereus strains (121 food- and 290 soil isolates) and 205 B. thuringiensis strains (43 serovars, 10 food- and 152 soil isolates). According to the presence of these eight toxin genes, they were divided into four groups among the total 616 isolates. In Group I, all eight genes occurred simultaneously in 403 (65.42%) isolates, while Group II (134 isolates or 21.75%) and Group III (46 isolates or 7.47%) were devoid of hblCDA and cytK, respectively. In Group IV, there were thirty-three isolates which lacked both hblCDA and cytK. The presence of hblCDA in B. thuringiensis strains (86.80%) was significantly higher (P<0.05) than in B. cereus strains (66.18%) whereas no significant difference in nheABC, cytK and entFM occurrence was detected between both bacterial groups. Both nheABC and entFM genes were found in all B. cereus and B. thuringiensis strains (616 strains in total), while the cytK gene could be detected in 365 (88.80%) of the B. cereus and 172 (83.90%) of the B. thuringiensis strains. None of the 616 tested strains showed the presence of only a single or two genes in either the hbl or nhe operons. The eight primer pairs designed for this multiplex PCR allowed rapid detection of eight toxin genes from boiled cells with high sensitivity, gave 100% reproducibility, and did not cross-react to 32 other bacterial strains.     

Biodiesel production from waste cooking palm oil using calcium oxide supported on activated carbon as catalyst in a fixed bed reactor

A reactor has been developed to produce high quality fatty acid methyl esters (FAME) from waste cooking palm oil (WCO). Continuous transesterification of free fatty acids (FFA) from acidified oil with methanol was carried out using a calcium oxide supported on activated carbon (CaO/AC) as a heterogeneous solid-base catalyst. CaO/AC was prepared according to the conventional incipient-wetness impregnation of aqueous solutions of calcium nitrate (Ca(NO₃)₂·4H₂O) precursors on an activated carbon support from palm shell in a fixed bed reactor with an external diameter of 60 mm and a height of 345 mm. Methanol/oil molar ratio, feed flow rate, catalyst bed height and reaction temperature were evaluated to obtain optimum reaction conditions. The results showed that the FFA conversion increased with increases in alcohol/oil molar ratio, catalyst bed height and temperature, whereas decreased with flow rate and initial water content in feedstock increase. The yield of FAME achieved 94% at the reaction temperature 60 °C, methanol/oil molar ratio of 25: 1 and residence time of 8 h. The physical and chemical properties of the produced methyl ester were determined and compared with the standard specifications. The characteristics of the product under the optimum condition were within the ASTM standard. High quality waste cooking palm oil methyl ester was produced by combination of heterogeneous alkali transesterification and separation processes in a fixed bed reactor. In sum, activated carbon shows potential for transesterification of FFA.     

Rapid transesterification of <Emphasis Type="Italic">Jatropha curcas</Emphasis> oil to biodiesel using novel catalyst with a microwave heating system

We used a microwave heating system to increase Jatropha biodiesel yield, and to reduce both reaction time and energy consumption. The feasibility of converting natural and non-edible feedstocks including arcuate mussel shells and dolomitic rocks, into a novel high-performance, reusable, low-cost and heterogeneous catalyst for the synthesis of biodiesel was also explored. Arcuate mussel shells and dolomitic rocks were first ground and calcined at 900 °C for 2 h. After calcination, calcium oxide (CaO) or a mixed oxide of calcium and magnesium (CaO·MgO) was obtained as white powder, which was then chemically activated to improve the physical, chemical and surface properties, and catalytic activities of the catalysts. By heating CaO from waste shells in an excess dehydrated methanol under 65 °C at 8 h with nitrogen (N₂) flow, calcium methoxide (Ca(OCH₃)₂) catalyst was prepared. The CaO from natural rocks was, however, turned into calcium glyceroxide complex, by combining with methanol and glycerol of the by-product. It was determined that calcium glyceroxide (Ca[O(OH)₂C₃H₅]₂) was formed during the transesterification and acted as the most active phase. Catalyst characterization was by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) surface area and basic strength measurements. The reaction parameters, including reaction time, microwave power, methanol/oil molar ratio, catalyst dosage and catalyst reusability, were studied for fatty acid methyl esters (FAME) yield. The results indicated that Ca(OCH₃)₂ and Ca[O(OH)₂C₃H₅]₂ catalysts derived from waste shells and natural rocks showed good reusability, high energy efficient, environmental-friendly, low cost and facile route for the synthesis of biodiesel.