The aim of this study was to evaluate the feasibility of biodiesel production by transesterification of Jatropha oil with methanol, catalyzed by non-commercial sn-1,3-regioselective lipases. Using these lipases, fatty acid methyl esters (FAME) and monoacylglycerols are produced, avoiding the formation of glycerol as byproduct. Heterologous Rhizopus oryzae lipase (rROL) immobilized on different synthetic resins and Carica papaya lipase (rCPL) immobilized on Lewatit VP OC 1600 were tested. Reactions were performed at 30°C, with seven stepwise methanol additions. For all biocatalysts, 51-65% FAME (theoretical maximum=67%, w/w) was obtained after 4h transesterification. Stability tests were performed in 8 or 10 successive 4h-batches, either with or without rehydration of the biocatalyst between each two consecutive batches. Activity loss was much faster when biocatalysts were rehydrated. For rROL, half-life times varied from 16 to 579h. rROL on Lewatit VPOC 1600 was more stable than for rCPL on the same support.
This work aims at evaluating the potential of Carica papaya lipase (CPL) self-immobilized in papaya latex as a biocatalyst for the synthesis of human milk fat substitutes (HMFS), to be used as a low-cost alternative to commercial lipases. Two different CPL preparations, one extracted from the papaya fruit (CPL I) and the other from petiole leaves (CPL II) of papaya tree, were tested as catalysts for the acidolysis between tripalmitin and (i) oleic acid or (ii) omega-3 PUFA, batchwise, at 608C, in solvent-free media. After 24 h, molar incorporation was higher for oleic acid (22.1 mol%) when CPL I was used. This biocatalyst was selected for further studies. RSM was used to model reaction conditions: medium formulation (molar ratio oleic acid/tripalmitin, MR, 1.2:1-6.8:1) and temperature (58-728C). Acyl migration decreased with MR increase. In batch operational stability assays at 608C, using MR of 2:1 and 6:1, the highest stability was observed for a MR of 2:1.Practical applications: The use of this biocatalyst is a feasible way to valorize papaya agro-residues which represent an important environmental problem in the producing countries. The obtained results were rather promising since, with this almost zero-cost biocatalyst, it was possible to produce a high added-value product (HMFS). Under optimized conditions, the obtained results were comparable with those obtained with expensive immobilized commercial lipases.
Cell wall recycling and β-lactam antibiotic resistance are linked in Enterobacteriaceae and in Pseudomonas aeruginosa. This process involves a large number of murolytic enzymes, among them a cytoplasmic peptidoglycan amidase AmpD, which plays an essential role by cleaving the peptide stem from key intermediates en route to the β-lactamase production (a resistance mechanism) and cell wall recycling. Uniquely, P. aeruginosa has two additional paralogues of AmpD, designated AmpDh2 and AmpDh3, which are periplasmic enzymes. Despite the fact that AmpDh2 and AmpDh3 share a common motif for their respective catalytic domains, they are each comprised of multidomain architectures and exhibit distinct oligomerization properties. We review herein the structural and biochemical properties of orthologous and paralogous AmpD proteins and discuss their implication in cell wall recycling and antibiotic resistance processes.
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