Mucor racemosus

The following strains were used throughout the study (all purchased from the American Type Culture Collection, ATCC): Streptomyces rimosus ATCC 10970, Streptomyces noursei ATCC 11455, Penicillium rubens ATCC 9178, Aspergillus niger ATCC 204447, Chaetomium globosum ATCC 6205, and Mucor racemosus ATCC 7924. The strains were maintained on agar slants according to the recommendations of ATCC.

In order to evaluate the antibacterial activity of propolis extracts, five strains of bacteria were used, selected from the main species found on cereals: Pseudomonas fluorescens (ATCC 13525), Bacillus subtilis (ATCC 6633), Bacillus cereus (ATCC 11788), Escherichia coli (ATCC 25922), and Proteus mirabilis (ATCC 7002). Antifungal activity was also evaluated using five strains of fungi from the species that contaminate cereals in the field, before harvesting: Alternaria alternata (TX 8025), Cladosporium cladosporioides (derived from ATCC 16022), Fusarium oxysporum (ATCC 48112), Mucor racemosus (derived from ATCC 42647), and Aspergillus niger (derived from ATCC 16888). All strains used were provided by Thermo Fisher Scientific Inc. (Waltham, MA, USA) and MicroBioLogics Inc. (St. Cloud, MN, USA).
In order to obtain bacterial cultures, 3–5 colonies from each bacterial strain were dispersed in 10 mL of nutrient broth (Mikrobiologie Labor-Technik, Arad, Romania) and were incubated for 18 ± 2 h, at 37 ± 1 °C. To obtain fungal cultures, colonies from each fungal strain dispersed in 10 mL of nutrient broth were incubated for 72 ± 2 h at 25 ± 1 °C. The turbidity of the cell suspension was measured using a McFarland Densitometer (Mettler Toledo, Columbus, OH, USA) and adjusted until the turbidity of the suspension was equivalent to the turbidity of a 0.5 McFarland standard.