Rev. Chim. ♦ 71 ♦ no. 2 ♦ 2020 ♦ https://revistadechimie.ro 248 https://doi.org/10.37358/RC.20.2.7922 Influence of pH on the Dehydrogenase Activity in Fusarium graminearum Species Schwb. Telemorph Gibberella Zeae (Schwb.) Petsch) Production of Mycotoxins PETRONELA GRADINARIU 1 , MARGARETA GRUDNICKI 2 , IOAN-MARIAN RISCA 2 *, VIOLETA MANGALAGIU 3 * 1 INDCSB, Biological Research Institute, 47 Lascar Catargi Str., 700107, Iasi, Romania 2 Stefan cel Mare University of Suceava, Forestry Faculty, 13 Universitatii Str., 720119, Suceava, Romania, 3 Alexandru Ioan Cuza University of Iasi, CERNESIM Research Center, 11 Carol Blvd., 700506, Iasi, Romania Dehydrogenases are enzymes that catalyzes the electron transfer reactions and act according to their redox potential (rH) from negative rH values to the highest positive ones. Depending on the chemical nature of the substrate which donates hydrogen, dehydrogenase bear appropriate names: α-ketoglutarate glucoso 6-fosfat dehidrogenase, isocitrate dehydrogenase, malate dehydrogenase, etc. The paper presents the influence of pH against the dehydrogenase activity, both if the mycelium and culture liquid, at 21 and 28 days from the inoculation. Keywords: oxidoreductase, dehydrogenase, enzymes The pH values, necessary for the growth of micro-organisms or for the production of certain substances biologically active ingredients, are parameters to be treated in the studies on the biology of the mold. Most of the micro-organisms grows at pH values between 5 to 9, between these extremes each has an optimal pH of action [1]. Previously, the effect of pH carried out on the activity of oxidoreductazes were studied on other species, such as: Aspergillus niger and Aspergillus tereus species, (Trichoderma viride, Mirothecium verrucaria [2], Chaetomium globosum [3-5]. Studies on the effect of pH on the activity of enzymes at the level of the patosystem ( Triticum aestivum-Fusarium graminearum) are few [6], establishing that the fungus needs for growing and developing pH values between 6 and 10. Fusarium graminearum requires, like all living organisms, chemical compounds necessary for the synthesis of cellular constituents, for the activity of enzymes and transport systems and for the energy supply of the entire organism [7,8]. The paper wants to highlight the influences of nature of hydrogen donor substrate and the pH against the enzymatic activity. Experimental part The determinations were made from the mycelium’s biomass resulting after the centrifugation of culture media. The determination method is based on the dehydrogenases capacity to transfer hydrogen from various substrates to the solution of 2,3,5-triphenyl tetrazolium chloride (TTC) which is reduced to red colored TTC formazan. The intensity of the color is proportional to the dehydrogenases concentration. For the dehydrogenases determination with exogenous substrate, samples have been maintained at a temperature of 28 ◦ C for 17 h. As exogenous substrate, solutions of known normality of glucose [9-11], natrium isocytrate [12, 13], α- ketoglutaric acid [14] and malate dehydrogenase [15, 16] were used. The color intensity of the TTC formazan was measured with a Perkin Elmer spectrophotometer. The enzyme activity was expressed as the amount of the resulting formazan, following the dehydrogenase action reported to the quantity of biological material of analysed (mycelium) [17]. The pH variations in the Fusarium graminearum culture media were studied in a range between 2.0 and 9.0. The Brown culture media was adjusted using NaOH 1N and HCl 0.1N. The determinations of biochemical parameters have been made at 21 and 28 days from seeding, in fungal mycelium and culture fluid. Al the date was expressed as μg formazan/g biological material. The data were statistically interpreted with the Student t test and the Pearson correlation coefficient (r), in order to determine whether there is an association between the two variables ( pH and oxidoreductases activity) and how strong this association is [18]. *email: risca@usv.ro; violetaren@yahoo.com