Otimização dos parâmetros fermentativos de Simplicillium lanosoniveum por meio da fermentação líquida submersa

Abstract

Simplicillium lanosoniveum is a biocontrol agent considered multi-action, as its isolates are known to be parasites of rust, have antibacterial, antifungal and antiviral activity, in addition to controlling plant pests. However, despite being frequently observed under field conditions, its commercial use is still quite limited, and the fermentation process may be one of the problems for its low availability in the market. For production viability, it is essential to obtain a high number of propagules. The search for alternative culture media in liquid fermentation, as well as production methods, is a necessity to enable its use on a large scale. Thus, the present work aimed to optimize the production process of Simplicillium lanosoniveum CMAA-1143 propagules through the nutritional composition in submerged liquid fermentation. To evaluate the effect of the C:N ratio and the ideal fermentation time as a function of time on the production of Simplicillium propagules, the basal medium proposed by Jackson et al. (1997), with different proportions of the C:N ratio (50:1; 30:1 and 10:1), glucose monohydrate as a carbon source and yeast extract as a nitrogen source. For this basal medium, the fermentation time was initially evaluated (48; 72; 96 hours after inoculation). The influence of aeration was evaluated using different final volumes (100 mL and 60 mL) in Erlenmeyer flasks. From this stage on, in all subsequent studies the production of propagules was evaluated on the 3rd day and the production of submerged conidia and microsclerotia was counted and the colony forming units (CFU) and biomass were determined. Different nitrogen sources were evaluated in mixture with glucose monohydrate as the main carbon source. After selecting the sources, the effects of the carbon sources combined with the selected N sources were evaluated. The effect of initial pH and preculture inoculum density were also evaluated. The ability of the isolate of S. lanosoniveum CMAA-1143 to solubilize phosphate and degrade chitin was also evaluated, and it was observed that the fungus did not solubilize phosphate, but degraded chitin. After selecting the best media, the growth kinetics of the propagules produced was evaluated by determining the pH for six days. The C:N ratio that showed the highest production of conidia was 50:1 with a total carbon of 36 g L-1. The initial pH did not influence the production of conidia. The combination of C and N sources established a production of 2,37 x 109 conidia mL-1 and 1,64 x 104 microsclerotia mL-1. Aeration was set to 250 rpm and preculture inoculum density to 1 x 104 conidia mL-1. Considering the benefits delivered by submerged liquid fermentation such as shorter fermentation time, high production of propagules, flexibility of the culture medium components, and other benefits, the results of the fermentation process of S. lanosoniveum CMAA-1143, of the present study, can collaborate with the biocontrol industry installed in Brazil.