Screening and detection of extracellular cellulases (endo- and exo-glucanases) secreted by filamentous fungi isolated from soils using rapid tests with chromogenic dyes

Abstract

The screening plate method is commonly used for previous detection of cellulases produced by microorganisms with biotechnological potential. In this manuscript, the authors aim to evaluate the hydrolytic ability of different fungi isolated from soil for the production of cellulolytic enzymes for cellulose degradation and determining the enzymatic index (EI) in relation to the growth of fungal colony and halo. The fungi were grown in carboxymethyl cellulose medium (CMC 1% w/v) and Avicel medium (Cellulose microcrystalline 1% w/v) for the determination of endo-glucanases and exo-glucanases respectively at 28°C for 48 h. Four chromogenic dyes were used: Congo Red, Phenol Red, Trypan Blue and Gram's Iodine. Also, another screening method was compared using carboxymethyl cellulose medium (CMC 1% w/v) at 28°C for 96 h and exposed with Congo Red dye in buffer Tris HCl 0.1 M, pH 8.0. The results obtained allowed to find significant differences between the tested fungi, the growth time and chromogenic dyes. The strains with higher Enzymatic Index (EI) were JCO1, UFT1, UFT2 and UFT3 for endo-glucanases and JCO2, UFT1, UFT2 and UFT3 for exo-glucanases.

Bioprospecting of endophytic fungi from semidesert candelilla (Euphorbia antisyphiliticaZucc): Potential for extracellular enzyme production

“…This can be attributed to the cellulose, hemicellulose, and lignin contents of the plant and the candelilla by‐products from which they were isolated, using these compounds as carbon sources for their growth. This information allowed us to infer that the capacity to produce extracellular enzymes varied among the isolated fungi, which was essential to classify and select those strains [41] that presented the highest PI values (Table 2).…”

“…These enzymes are used in various applications; xylanases are applied in the feed industry [58], amylases in the textile industry to separate fibers, and cellulases for fruit liquefaction [59]. In addition, PI values for Trichoderma and Neurospora generans of 0.89 and 0.8, respectively [41,60], have also been reported; these fungi have been used to produce cellulases, which are used in the beverage industry [61]. However, there are few studies on these types of microorganisms in terms of their potential to express laccase.…”

Potential of marine sponge-derived fungi in the aquaculture system

“…Gram's iodine stain (2.0 g KI and 1.0 g iodine in 300 mL distilled water) was used as a hydrolysis indicator. On the last day of the incubation, CMC plates and soluble agar were flooded with a 10 mL Gram's iodine stain for 10 min (Colonia and Junior 2014). The amylase activity was determined by the starch hydrolysis, which can be seen in the presence of hydrolysis zone around the fungal plate colony (Lübeck and Lübeck 2018).…”

Antimicrobial activities of Plantactinospora sp. KBS50, a rare marine-derived actinomycete from the coastal area of Sarawak

“…The actinomycete strain KBS50 was spot inoculated onto the SMA, CMC and Avicel agar test plates, and incubated at 28 °C for up to fourteen days. Glucanase activity was detected using Congo red solution as an indicator (Sazci et al, 1986;Brigitte and Aloisio, 2014). Meanwhile, the production of proteases was determined from the formation of a clear zone around the actinomycete colony on skim milk agar (Rydén et al, 1973;Alnahdi, 2012).…”