Abstract
This research examined the potential use of isolated Serbian autochthonous fungi in lignocellulosic biomass pretreatment. Among 12 isolated fungi, the isolates identified as Trametes hirsuta F13 and Stereum gausapatum F28 stood out as ligninolytic enzyme producers and were selected for potential use in the pretreatment of a waste lignocellulosic biomass. An isolate identified as Myrmaecium fulvopruinatum F14 showed high hydrolytic activity, but negligible ligninolytic activity, and it was selected as a potential producer of important industrial hydrolytic enzymes. Further, the breakdown of lignocellulosic waste, beechwood sawdust, by T. hirsuta F13 and S. gausapatum F28 was examined. Both isolates efficiently degraded biomass, but T. hirsuta F13 exhibited greater selectivity (selectivity coefficient of 1.7) than S. gausapatum F28 (1.1). The isolate F13 was considered a better candidate for the pretreatment, and it was selected for further analysis which involved the use of molasses stillage as a supplement to improve the pretreatment.
Highlights
Lignocellulosic waste as a renewable resource has attracted attention as a potential substrate for the production of valueadded chemicals, but its complex structure prevents its direct use; it needs to be pretreated to remove lignin and hydrolyzed before it could be used, which can be done by chemical, physical, physicochemical, or biological methods (Gauna et al, 2018; Nair and Sivakumar, 2020; Vučurović et al, 2019)
Laccase activity was measured using guaiacol assay (Abd El Monssef et al, 2016; Jović et al, 2018), manganese peroxidase and versatile peroxidase activities were determined with phenol red (Arora and Gill, 2005; Jović et al, 2018; Kuwahara et al, 1984), lignin peroxidase activity with azure B (Archibald, 1992; Jović et al, 2018), and cellulase and xylan activities were determined by the Miller's DNS method (Jović et al, 2020; Miller, 2002)
Among the 12 isolated fungi, the best ligninolytic activity showed two isolates, F13 and F28 (Figure 1 and 2), which were identified as Trametes hirsuta F13 and Stereum gausapatum F28, respectively
Summary
Lignocellulosic waste as a renewable resource has attracted attention as a potential substrate for the production of valueadded chemicals, but its complex structure prevents its direct use; it needs to be pretreated to remove lignin and hydrolyzed before it could be used, which can be done by chemical, physical, physicochemical, or biological methods (Gauna et al, 2018; Nair and Sivakumar, 2020; Vučurović et al, 2019). The biggest disadvantage of this method is the long pretreatment time, which can be 1-3 months, as well as the loss of a certain amount of sugar – an integral part of lignocellulosic biomass – required for fermentation processes (Mielenz, 2020; Zhang et al, 2020). These limitations can be overcome or mitigated by the use of organisms that efficiently degrade biomass, primarily by the use of selective decomposers, as well as by formulating the conditions that would improve the pretreatment process by shortening its duration and reducing the loss of necessary sugars. Fungi that belong to the genera Trametes, Ganoderma, Pleurotus have proved to be good candidates for lignocellulose pretreatment use (Gauna et al, 2018; Isroi et al, 2011)
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