Biodegradation and Micro- Scale Treatability Pattern of Loblolly Pine Heartwood Bioincised by Bacillus Subtilis and Physisporinus Vitreus

Abstract

One strategy for improving the treatability of refractory wood species is biological incising, and its efficiency depends on how the microorganisms modify the porous structure of the wood. Evaluation of the bioincised wood treatability on a micro-scale can thus help to better understand the treatability enhancing mechanisms. In the present study, the biodegradation pattern and micro-scale treatability of Loblolly pine (Pinus taeda L.) heartwood were determined after bioincising with the white-rot fungus Physisporinus vitreus (Pers.: Fr.) P. Karsten isolate 136 and bacterium Bacillus subtilis UTB22. Oven-dried specimens with dimensions of 50 mm × 25 mm × 15 mm (L × T × R) were incubated with the microorganisms at (23±2) °C and (65±5) % relative humidity for six weeks. The control and exposed wood blocks were then pressure treated by 1 % fluorescent dye (fluorescein)-containing water to study the treatability pattern under a fluorescence microscope. The longitudinal and tangential air permeability and compression strength parallel to the grain of the specimens were also determined at the end of the incubation period. Scanning electron microscopic (SEM) studies showed that degradation by B. subtilis UTB22 was limited to the pit membranes, but the cell walls were also degraded to some extent by P. vitreus. The fungus caused a higher mass loss compared to the bacterium, whereas the permeability enhancing ability of the bacterium was more pronounced. The fluorescent dye tracer also showed that higher treatability with more uniformity was obtained by B. subtilis UTB22. The improvement in treatability by both microorganisms was mainly due to the degradation of the earlywood tracheids.

Anatomical structure and copper microdistribution in mechanical, biological, and laser incised spruce and larch refractory woods

“…To better understand this case, extensive wood chemistry analyses are needed for the type and amount of wood chemical components degraded after P. vitreus fungal activity. Although many studies have been conducted on the effects of P. vitreus fungus on the permeability, physical, mechanical, and anatomical properties of wood (Lehringer et al 2010;Lehringer 2011;Lehringer et al 2011;Fuhr et al 2012;Gilani et al 2014;Emaminasab et al 2016;Bakir et al 2021;Tajrishi et al 2021;Bakir et al 2022aBakir et al ,b, 2022a, studies on wood chemical components seem to be limited.…”

“…However, there is still considerable speculation and debate about the relative effectiveness and future of each of these parameters on the physical, mechanical, chemical, and anatomical properties of wood. Numerous studies have been carried out to increase the permeability of wood species that are difficult to impregnate using various techniques; however, there are limited studies on the comparative effects of these different incision pretreatments (Tajrishi et al 2021;Bakir 2022a,b).…”