Enzymatic Biocatalysis Of Bamboo Chemical Constituents To Impart Anti-Fungal Properties

The current anti-fungal agents that capitalize on broad spectrum biocidal toxicity for their efficacy,can create potential hazards in the environment as in many cases they are not chemically bonded to the bamboo/wood thus,leach into the various ecosystems and jeopardize off-target organisms.In this study,laccase bio-catalysis of potassium iodide was used to impart non-diffusible anti-mold and decay properties to4-year old Phyllostachys pubescens bamboo.The mechanisms of how this system works against fungal strains of Aspergillus niger?A.niger?,Trichoderma viride?T.viride?,Penicillium citrinum?P.citrinum?,Gloeophyllum trabeum?G.trabeum?and Trametes versicolor?T.versicolor?were studied.Laccase activity test was determined at room temperature by using PBS buffer and various formulations of laccase and ABTS in transparent cuvettes and pipette.Likewise,the tests to reveal the effectiveness of laccase-catalyzed oxidation of potassium iodide and potassium iodide alone on treated bamboo against mold and decay fungi were carried out according to ASTM D 4445-03,AWPA E 24–06,AWPA E 24–12 and ASTM D1413-99correspondingly.Fourier transform infrared spectroscopy?FTIR?and X-ray photoelectron spectroscopy?XPS?analyses were used to investigate the sample chemistries,and mechanisms respectively.While,ICP-MS was used to determine the amount of iodine fixed onto the major constituents of bamboo,SEM scrutinized the movement of mycelia within and destruction of the unit sample structures.The color categorization before and after sample exposure to ultraviolet irradiation was done by using a laboratory digital colorimeter DC-PC3.The results revealed that laccase was more effective under temperature 40°C,pH=5 for 20 h,and its activity increased with increased amounts of ABTS.Besides,the treatment combination of 2.5 wt.%KI,18.0 mg/L ABTS and 0.60 U/mL laccase was most effective against both mold and decay fungi.Again,lignin samples showed the greatest changes in FTIR than hemicellulose and cellulose after biocatalyzed KI modification.The binding energy readings from 3d XPS spectra of 621.1 and 632.7eV?Aromatic region?obtained for lignin were consistent with I-C binding associated with its phenolic structures.While the 620.7 eV?Aliphatic region?suggested I-C bonding that occurred with iodine being chemically linked to lignin residue in hemicellulose,no peaks were observed for cellulose.From ICP-MS test,after leaching with water for 14 days,10.46 mg/g and only5.17 mg/g leached out from KI alone and laccase catalyzed KI treated samples respectively indicating that the presence of laccase accelerated the fixation of iodine onto bamboo.Also,the fungal resistance followed the trend Trichoderma viride?T.viride?>Penicillium citrinum?P.cintinum?>Aspergillus niger?A niger?and Trametes versicolor?T.versicolor?>Gloeophyllum trabeum?G.trabeum?.The average percentage weight losses were 7.92,11.75 and 18.75?unleached?and 9.44,14.3 and24.95?unleached?for laccase-KI,KI and control samples for Trametes versicolor?T.versicolor?and Gloeophyllum trabeum?G.trabeum?separately.The SEM results showed that Trametes versicolor?T.versicolor?colonized cells via apertures of simple or bordered pits which were then enlarged while Gloeophyllum trabeum?G.trabeum?degradation ensued within lignified cell walls in the order of control>KI>laccase-KI.When the treated samples were irradiated with UV,improved resistance against fungal attack was noted and the average percent weight loss was in the order of 4.79?laccase-KI?>8.7?KI?>11.83?control?,and 9.09?laccase-KI?>14.23?KI?>17.73?control?for Trametes versicolor?T.versicolor?and Gloeophyllum trabeum?G trabeum?correspondingly.Likewise,the FTIR results revealed clear changes in the lignin aromatic lignin peaks like those at 1513 cm^-1,1463 cm^-1conversely,other new carbonyl groups were formed at 1735 cm^-1,confirming sample surface photo oxidation hence slight net color changes??E*?were observed.The enzyme-catalyzed formation of I-C bonds with bamboo chemical constituents proved to be a highly effective and ecological method to protect bamboo against fungal colonization,hence needs to scaled up to avert the use of toxic chemicals in bamboo industry to minimize environmental degradation.