A proton NMR study of the glycine-mercury(II) system in aqueous solution

The proton NMR spectrum of glycine was monitored in D2O solution as a function of added Hg(II) concentration and pD. Reliable values were established for formation constants for the Hg(II):glycine 1:1 and 1:2 complexes and also for the mixed glycine/deuteroxy and glycine/chloride complexes. Ligand exchange kinetics are relatively slow, and it is possible to observe coupling to 199Hg through the coordinating nitrogen. The formation constants were used to calculate speciation over a range of ligand concentrations for the Hg(II)/glycine and Hg(II)/glycine/chloride systems.     

Suitability of aspenwood biologically delignified with Pheblia tremellosus for fermentation to ethanol or butanediol

Summary Enzymatic conversion of lignocellulosic material to fuels and chemicals depends on a initial pretreatment to render the cellulose more susceptible to enzymatic attack. Biological delignification of aspenwood with the fungus Phlebia tremellosus was compared to steaming as a pretreatment method.The biologically delignified aspenwood (BDA) had a high pentosan content and did not contain inhibitors of enzymatic hydrolysis or subsequent fermentation. In contrast, the steamed aspenwood required a water extraction step to remove the inhibitory material and this step also removed most of the pentosan. The yield of treated material was 90% from biological delignification and 70% from steaming.The cellulose in the BDA was less accessible to the cellulase enzymes than the steamed aspenwood. Combined hydrolysis and fermentation with Saccharomyces cerevisiae gave a lower yield of ethanol from BDA than from the steamed aspenwood, but the yields based on the weight of substrate before pretreatment were comparable. Combined hydrolysis and fermentation with Klebsiella pneumoniae gave higher yields of butanediol from BDA than from steamed aspenwood, because Klebsiella can ferment the xylose which was present in the biologically treated aspenwood. Trichoderma harzianum produced lower levels of cellulase enzymes when grown on BDA than when grown on steamed aspenwood and this was related to the xylan found in the biologically treated material.Abbreviations BDA biologically delignified aspenwood - SEA-WI steam-exploded, water-extracted aspenwood - AI-SEA-WI acid-impregnated, steam-exploded, water-extracted aspenwood - CHF combined hydrolysis and fermentation - FP filter paper