Application of a Posttreatment to Improve the Viability and Antifungal Activity of Trichoderma asperellum Biomass Obtained in a Bioreactor during Submerged Cultivation

SIMPLE SUMMARY: Trichoderma spp. are common soil microorganisms that play an important role in limiting phytopathogenic microorganisms, improving plant growth and degrading plant biomass. Often the determining factors affecting the growth and maintenance of viability of Trichoderma spp. are the composition and condition of the growth medium. This study provides information on post-treatment procedures that would improve the viability of T. asperellum biomass and the antifungal activity obtained from submerged cultivation in a bioreactor. The aim of the study was to determine the viability of fungal biomass and competitiveness against a phytopathogen after treatment with hydrochloric acid, copper (II) sulphate and starch, alone or in combination. ABSTRACT: T. asperellum MSCL 309 was used in the study. T. asperellum was grown in the stirred bioreactor under submerged cultivation. The resulting biomass was filtered to obtain a thick biomass. The viability and antifungal activity of T. asperellum biomass samples were determined simultaneously by studying the colonization of the malt extract agar medium surface and its competitiveness with the plant pathogenic fungus Fusarium graminearum using in vitro dual culture experiments. Treatment with starch, alone or in combination with copper (II) sulphate and/or hydrochloric acid did not significantly affect fungal viability compared to control. An important factor in maintaining viability was the addition of hydrochloric acid, which significantly increased the storage life of biomass. In all post-treatments, F. graminearum was overgrown with T. asperellum in seven days, and accordingly, the larger the area occupied by T. asperellum, the smaller the area of F. graminearum colonization. Viability and antifungal activity of T. asperellum persisted throughout the experiment, at least for eight weeks. All the post-treatment methods we studied improved the viability and antifungal activity of Trichoderma, at least in terms of the area of the colonized surface. For the development of long-term viable and active T. asperellum preparations, we recommend the use of acidification of T. asperellum biomass obtained by submerged fermentation.