Correlation between Agar Plate Screening and Solid-State Fermentation for the Prediction of Cellulase Production by Trichoderma Strains

Abstract

The viability of converting biomass into biofuels and chemicals still requires further development towards the reduction of the enzyme production costs. Thus, there is a growing demand for the development of efficient procedures for selection of cellulase-producing microorganisms. This work correlates qualitative screening using agar plate assays with quantitative measurements of cellulase production during cultivation under solid-state fermentation (SSF). The initial screening step consisted of observation of the growth of 78 preselected strains of the genus Trichoderma on plates, using microcrystalline cellulose as carbon source. The 49 strains that were able to grow on this substrate were then subjected to a second screening step using the Congo red test. From this test it was possible to select 10 strains that presented the highest enzymatic indices (EI), with values ranging from 1.51 to 1.90. SSF cultivations using sugarcane bagasse and wheat bran as substrates were performed using selected strains. The CG 104NH strain presented the highest EGase activity (25.93 UI·g−1). The EI results obtained in the screening procedure using plates were compared with cellulase production under SSF. A correlation coefficient (R 2) of 0.977 was obtained between the Congo red test and SSF, demonstrating that the two methodologies were in good agreement.

Application of semi-quantitative and quantitative methods for the selection of cellulolytic filamentous fungi isolated from pulp mill materials

“…For cellulase activity determination, at the next selection stages, various cellulose types were applied: Servacel (Goldbeck et al, 2012); Whatman No. 1 filter paper (Ruegger and Tauk-Tornisielo, 2004;Jahangeer et al, 2005;Florencio et al, 2012); and wheat bran (Ruegger and Tauk-Tornisielo, 2004;Damaso et al, 2012;Florencio et al, 2012). Application of cellulose with different physicochemical properties can affect the activity of cellulases.…”

“…At this stage, only few samples are subjected to a quantitative evaluation. Sazci et al (1986) and Florencio et al (2012) showed a correlation between the results obtained by semiquantitative and quantitative methods, but Goldbeck et al (2012) and Damaso et al (2012) pointed out that EI could not discern between isolates with different cellulase activities.…”

“…At the first stage, the isolates that can grow on a medium with cellulose as the only source of carbon are preselected (Florencio et al, 2012). At the second stage, the isolates with no cellulose hydrolysis zone around the colony (then EI values cannot be calculated) (Jahangeer et al, 2005;Goldbeck et al, 2012) as well as those whose EI is below a predefined value are rejected.…”

“…At the second stage, the isolates with no cellulose hydrolysis zone around the colony (then EI values cannot be calculated) (Jahangeer et al, 2005;Goldbeck et al, 2012) as well as those whose EI is below a predefined value are rejected. Damaso et al (2012) set the threshold to 1.0, Florencio et al (2012) to 1.5, and Lopes et al (2011) to 2.5. At this stage of semiquantitative appraisal, some Trichoderma species with no EI determined but with the highest EG activity can be omitted (Ruegger and Tauk-Tornisielo, 2004).…”

Antibacterial Activity of Three Streptomyces Species Isolated From Soils of Shikaripura, Karnataka, India

“…Biochemical tests viz., starch hydrolysis, gelatin liquefaction, casein hydrolysis, catalyst test, citrate test, cellulose hydrolysis, nitrate reduction test, hydrogen sulfide (H 2 S) production test and sugar fermentation test were performed 7,8 .…”