Pablo López-Albarrán

Molecular docking insights into the inhibition of laccase activity by medicarpin

Molecular docking calculations were performed to understand the inhibition mechanism of medicarpin on the lignin degradation enzyme laccase. The study was carried out in two stages. The first stage was performed on a laccase–oligolignol complex, to elucidate the active binding mode in the enzyme that initiates lignin degradation. The second stage was performed on a laccase–medicarpin complex, to understand the inhibitory effect of medicarpin on the enzymatic mechanism. In this two-step procedure, the crystal structure of a laccase (PDB: 1GYC) obtained from Trametes versicolor, a white-rot fungus capable of degrading lignin in wood, was employed because it produces considerable amounts of laccase. The results obtained from the laccase–oligolignol complex indicate that the binding site is located in a pocket that surrounds the T1 copper atom, which is in agreement with experimental reports. The results from the laccase–medicarpin complex indicate that the inhibitory effect occurs by the blockage of a solvent channel in the T. versicolor laccase by a medicarpin conformer, preventing the rapid access of molecular oxygen to the trinuclear T2/T3 copper cluster, and also by the coupling of medicarpin conformers in the T1 site pocket, blocking access by oligolignol molecules. Therefore, this coupling of medicarpin to two sites in laccase interrupts the enzymatic mechanism of lignin degradation. The results of this study may be useful in developing wood-preserving formulations based on medicarpin or similar molecular structures and in expanding the scientific knowledge of laccase activity for biotechnological applications.

Comparison of five pretreatments for the production of fermentable sugars obtained from Pinus pseudostrobus L. wood

To benefit from the use of a waste product such as pine sawdust from a sawmill in Michoacán, Mexico, five different pretreatments for the production of reducing sugars by enzymatic hydrolysis were evaluated (sodium hydroxide, sulfuric acid, steam explosion, organosolv and combined method nitric acid / sodium hydroxide). The main finding of the study was that the pretreatment with 6 % HNO3 and 1 % NaOH led to better yields than those obtained with sodium hydroxide, dilute sulfuric acid, steam explosion, and organosolv pretreatments. Also, HNO3 yields were maximized by the factorial method. With those results the maxima concentration of reducing sugar found was 97.83 ± 1.59, obtained after pretreatment with 7.5 % HNO3 at 120 °C for 30 minutes; followed by 1 % of NaOH at 90 °C for 30 minutes at pH 4.5 for 168 hours with a load enzyme of 25 FPU/g of total carbohydrates. Comparing the results obtained by the authors with those reported in the literature, the combined method was found to be suitable for use in the exploitation of sawdust.

Chemical composition of biomass generated in the guava tree pruning

Psidium guajava L. (Myrtaceae) is a native plant of Central America and is now widely cultivated in many tropical regions of the world for the fruit production. In Mexico, in the guava orchards common practices to control fruit production are: water stress, defoliation and pruning. In this study, we report the chemical composition of the biomass (branches and leaves) generated in the pruning practices. The results ranged as follows: pH (4.98-5.88), soda solubility (39.01-70.49 %), ash (1.87-8.20 %); potassium and calcium were the major inorganic elements in ash. No heavy metals were detected in the studied samples; total solubility (15.21-46.60 %), Runkel lignin (17.77-35.26 %), holocellulose (26.56 -69.49 %), α-cellulose (15.53-35.36 %), hemicelluloses (11.02-34.12 %), tannins in aqueous extracts (3.81-9.06 %), and tannins in ethanolic extracts (3.42-15.24 %).

La bacteria Arthrobacter agilis UMCV2 y diversas aminas inhiben el crecimiento in vitro de hongos destructores de madera

The kingdom Fungi is represented by a large number of organisms, including pathogens that deteriorate the main structural components of wood, such as cellulose, hemicellulose and lignin. The aim of our work was to characterize the antifungal activity in Arthrobacter agilis UMCV2 and diverse amines against wood-decaying fungi. Four fungal organisms (designated as UMTM) were isolated from decaying wood samples obtained from a forest in Cuanajo-Michoacán, México. Two of them showed a clear enzymatic activity of cellulases, xylanases and oxido-reducing enzymes and were identified as Hypocrea (UMTM3 isolate) and Fusarium (UMTM13 isolate). In vitro, the amines showed inhibitory effect against UMTM growth and one of the amines, dimethylhexadecylamine (DMA16), exhibited strong potential as wood preventive treatment, against the attack of decaying fungi.