Morphological and enzymatic response of the thermotolerant fungusFomessp. EUM1 in solid state fermentation under thermal stress

Abstract

Thermotolerance of the fungus Fomes sp. EUM1 was evaluated in solid state fermentation (SSF). This thermotolerant strain improved both hyphal invasiveness (38%) and length (17%) in adverse thermal conditions exceeding 30°C and to a maximum of 40°C. In contrast, hyphal branching decreased by 46% at 45°C. The production of cellulases over corn stover increased 1.6-fold in 30°C culture conditions, xylanases increased 2.8-fold at 40°C, while laccase production improved 2.7-fold at 35°C. Maximum production of lignocellulolytic enzymes was obtained at elevated temperatures in shorter fermentation times (8-6 days), although the proteases appeared as a thermal stress response associated with a drop in lignocellulolytic activities. Novel and multiple isoenzymes of xylanase (four bands) and cellulase (six bands) were secreted in the range of 20-150 kDa during growth in adverse temperature conditions. However, only a single laccase isoenzyme (46 kDa) was detected. This is the first report describing the advantages of a thermotolerant white-rot fungus in SSF. These results have important implications for large-scale SSF, where effects of metabolic heat are detrimental to growth and enzyme production, which are severely affected by the formation of high temperature gradients.

Heat stress on Fomes culture reduces proteases and improves laccases thermostability

“…Finally, 50 mL of 50 mM ABTS in 50 mM citrate buffer (pH 5) was added, and gels were incubated at 40 °C for approximately 20 min. to reveal the bands with laccase activity (Ordaz-Hernández et al, 2016).…”

“…The genus Fomes is capable of degrading lignin being laccases one of the enzymes responsible for this process and hence the various reports on the production of this enzyme by various species of this genus (Neifar et al, 2010;Papinutti et al, 2003;Papinutti et al, 2006;Papinutti et al, 2008;Vȇtrovský et al, 2013). Most fungal species of the genus Fomes are mesophilic, with an optimal growth temperature between 20 and 36 °C; although, a thermotolerant strain has been reported (Ordaz-Hernández et al, 2016). This strain of Fomes sp.…”

“…Many organisms change the fatty acid composition of their membrane for the optimal functioning of transporters and enzymes to grow at high temperatures (Ianutsevich et al, 2016). Temperature stress causes enzymatic responses, e.g., protease production has been observed in thermophilic and thermotolerant organisms (Ordaz-Hernández et al, 2016;Walker and White, 2017). Temperature stress is also related to protein glycosylation that stabilizes protease attacks and protein secretion (Chatterjee et al, 2018).…”

Cellulase Production by Aspergillus niger ATCC 16888 on Copra Waste from Coconut Milk Process In Layered Packed-bed Bioreactor

“…When the temperature reached around 50 °C, the growth stopped and then decreased (death phase), because the fungal hyphal branching decreased at the temperature higher than 45 °C 37 . After the growth had stopped, the temperature of all beds decreased due to a decrease in heat generation from fungal respiration 38 . The decrease in glucosamine content indicated self-degradation of fungi, where the fungal cell was destroyed by many fungal self-produced enzymes, including cellulase 39 .…”

Production of extracellular enzymes by a termite‐nest‐related Bacillus siamensisYC‐9 in solid‐state fermentation on agricultural by‐products

“…The application of SSF technology could be an effective process for such bioconversions. Much research has shown that the properties of enzymes produced in this way exhibited higher productivity and superior performance 11, 12 . Moreover, SSF is an economical process, because agro‐industrial wastes could be used as a cheaper substrate 8, 13 .…”