Effect of dilute acid pretreatment severity on the bioconversion efficiency of Phalaris aquatica L. lignocellulosic biomass into fermentable sugars.

The effect of dilute acid pretreatment severity on the bioconversion efficiency of Phalaris aquatica lignocellulosic biomass into fermentable sugar monomers was studied. The pretreatment conditions were expressed in a combined severity factor (CSF), ranged from 0.13 to 1.16. The concentration of xylose and total monomeric sugars released from hemicellulose increased with pretreatment as the CSF increased. Dilute acid pretreatment resulted in about 1.7-fold increase in glucose release relative to the untreated biomass, while CSF was positively correlated with glucose recovery. A maximum glucose yield of 85.05% was observed at high severity values (i.e. CSF 1.16) after 72 h. The total amount of sugars released (i.e. xylose and glucose) was increased with pretreatment severity and a maximum conversion efficiency of 76.1% of structural carbohydrates was obtained at a CSF=1. Our data indicated that Phalaris aquatica L. is an alternative bioethanol feedstock and that hemicellulose removal promotes glucose yield.

Contamination of honey by chemicals applied to protect honeybee combs from wax-moth (Galleria mellonela L.).

Greek honey was monitored during a three-year surveillance program for residues of chemicals used to protect honey-bee combs from wax-moth. A total of 115 samples purchased from stores (commercial samples) and 1060 samples collected from beekeepers (bulk samples) were analysed for 1,4-dichlorobenzene (p-DCB), 1,2-dibromoethane (DBE) and naphthalene. A purge & trap-gas chromatograph-mass spectrometer system was used for the analysis. During the first year of the study, 82.9% of the commercial samples had residues of p-DCB that exceeded the established limit of 10 microg kg(-1), whilst during the second year 53.6% and during the third 30% exceeded the limit. The percentage of beekeepers samples that had more than 10 microg kg(-1) decreased from 46.6 to 34.7% and 39.8% respectively during the three consecutive years of analysis. Only one commercial sample (0.8%) had residues of DBE that exceeded 10 microg kg(-1) during the three years study, while 9.9% of the beekeepers samples exceeded this limit in 2003. This percentage fell to 1.9 and 2.8% during the following years. Naphthalene was found in more commercial samples than in samples from beekeepers during the first year, but decreased to similar levels during the next two years. Honeys that are produced earlier in the season are more contaminated those produced later.

Determination of 1,2-dibromoethane, 1,4-dichlorobenzene and naphthalene residues in honey by gas chromatography--mass spectrometry using purge and trap thermal desorption extraction.

A highly sensitive method for the determination of 1,2-dibromoethane, 1,2-dichlorobenzene and naphthalene residues in honey was developed, using gas chromatography-mass spectrometry combined with a purge and trap thermal desorption system as the extraction technique. Optimal conditions for isolation and separation were established and calibration curves were constructed. Linearity was held between 2.4 and 300 microg kg(-1) honey for 1,2-dibromoethane, 0.5 and 300 microg kg(-1) for 1,4-dichlorobenzene and 0.125 and 3000 microg kg(-1) for naphthalene. The detection limits were found to be 0.8, 0.15 and 0.05 microg kg(-1) honey for 1,2-dibromoethane, 1,4-dichlorobenzene and naphthalene, respectively. The method was applied to the analysis of 25 Greek honey samples. 1,2-Dibromoethane was not found in the majority of the samples, while only one sample was found to contain both 1,4-dichlorobenzene and naphthalene residues at concentrations exceeding 10 microg kg(-1).