## 1 Introduction  
Wood, as a natural organic material, consists of hemicellulose, cellulose, lignin, and minor amounts of organic extractives, as well as ash as an inorganic mineral [1]. Wood is susceptible and readily degraded by bacteria, fungi, and termites [2; 3; 4]. In particular, wood is attacked by fungi when the conditions are suitable, such as a high wood moisture content (>20%), the presence of oxygen, and temperatures in the range of 25-40\({}^{\circ}\)C [5]. Fungi colonize wood by degrading the components of the cell wall to form brown, soft, or white rot. Within the cell wall, discrete cavities are formed as soft-rot fungi erode the secondary wall [6]. Sapwood is more susceptible to fungal attack than heartwood, because of the higher concentration of sugars and carbohydrates. Extractives in the heartwood are key in order to make the wood unpalatable to destroying organisms as well as for the prediction of the durability of wood [7]. The C and O element compositions of _Acacia saligna_ wood affected by the fungi _Trichoderma harzianun_, _Alternaria tenuissima_, and _Fusarium cultorun_ are decreased compared with the control treatment (unincubated) [8; 9]. Cellulase enzymes, such as those derived from the lignocellulosic fungi of the species _T. reesei_, _Aspergillus niger_, _A. nidulans_, and _Penicillium funcilulosum_, are more selective and competitive to hydrolyze cellulose into monosaccharides, such as glucose [10]. [PERSON] and [PERSON] [11] recommended adding stains of soft-rot fungi (_A. niger_, _P. chrysogenum_, and _Chaetomium globosum_) and surface molds (_T. viride_ and _A. alternate_) to the wood-destroying fungi classification, in addition to recommending examining their enzymatic systems. In pine and sycamore wood, [PERSON] [12] proved that _A. niger_ produced cavity formation as a decaying type I soft-rot and type II (erosion), while _P. chrysogenum_ caused type II decaying from as wood degradation in the soil. _T. viride_, as a surface mold, was reported to colonize parenchyma cells and to consume the contents of the nutrients in these cells enzymatically, but not to decompose wood [13]. Fungi play a potent role in wood degradation by increasing the contents of organic acids, and for obtaining nutrients, fungi release extracellular enzymes and acids, and then break down the materials prior to their absorption, releasing microbial degraded materials, gases, or microbial volatile organic compounds (MVOCs) into the environment [14; 15]. An increase in organic acids leads to accelerating the degradation of wood. Many fungi, including both the brown and white rot fungi, produce calcium oxalate crystals that adhere to the hyphae [16; 17]. Oxalate-producing white rot species (_Bjerkandera fumosa_, _C. unicolor_, and _Phlebia radiate_) and a brown rot species (_Fomitopsis pinicola_) have been studied for calcium oxalate crystal formation [18]. Oxalic acid production by brown-rot decay fungi has eluded many researchers for decades [19; 20; 21]. This is then followed by the secretion of hydrolytic enzymes that decompose the polysaccharides' plant cell wall [22; 23]. Also, it plays an indirect role in the initiation of the decay process, which reduces the viscosity of the hemicellulose and cellulose [24; 25; 26]. _Antrodia vailantii_ was suggested for the accumulation of significant quantities of oxalic acid when inoculated in copper citrate-treated Southern pine [27]. After a 10-day fermentation process, _A. niger_ and _Rhizopus javanicus_ showed a high oxalic acid production [28]. Acetic acid in wood vinegar has been reported to have fungicidal properties, and can be used as an insect repellent, an odor remover, and as a wood preservative instead of other traditional chemicals [29; 30]. The pH decreased from 5.5 to 4.0 during the fermentation process of wheat straw, which indicates the production of organic acids by the white rot fungus _Nematoloma frovardii_, where malate, fumarate, and oxalate were present at a high level [31].