Perfil enzimático e de resistência a antimicrobianos de espécies de Bacillus associados a microalga Arthrospira platensis

Abstract

Algae culture is the algae and microalgae production and it has been increasing in global scale, producing 35,1 million of tonnes of biomass only in 2020. It is the interest target for many industries like cosmetics, food and pharmaceutics. The most comercially cultivated microalgae is the blue-green cyanobacteria Spirulina (Arthrospira platensis), which has a lot of concentration of benefits in the composition. This cyanobacteria lives in association with other microrganisms such as bacteria of Bacillus genus, known for its great probiotic potential. Mutations occur naturally when the bacterial population is exposed to certain antimicrobials. Therefore, this research aims to identify species and evaluate resistant strains of Bacillus isolated from a spirulina culture located in Fortaleza, Ceará. Biochemical tests were performed, such as Gram staining, motility, production of indole and hydrogen sulfide (H2S), citrate, Voges Proskauer, nitrate reduction and enzymatic profile tests such as catalase, amylase, caseinase, gelatinase, lecithinase and urease for phenotypic characterization. From colonies freshly grown on TSA (Tryptic Soy Agar) agar culture medium, 40 strains were isolated, identified as belonging to the genus Bacillus; Bacillus sp. (n = 11); 13 species as: B. stearothermophilus (n = 6), B. macerans (n = 4) B. panthotenicus (n = 4), B. popillae, (n = 3), B pasteurii (n = 2), B. circulans (n = 2), B. coagulans (n = 2), B. licheniformis (n = 1), B. badius (n = 1), B. subtilis (n = 1), B. megaterium (n = 1), B. sphaericus (n = 1), B. polymyxa (n = 1). Twenty one strains showed enzymatic activity for starch hydrolysis (78,5%), ten for hydrolysis of casein (50%), twenty for lecithinase (62,5%) and five for gelatinase (20%). The highest rates of antibiotic resistance detected were for streptomycin with 14 (48,2%) resistant strains, followed by erythromycin with 5 (17,4%), ampicillin with only 1 resistant strain (3,5%). All strains were sensitive to chloramphenicol (100%), which gives the drug greater effectiveness. Thus, more research will be needed to verify the probiotic efficiency of the analyzed strains and their resistance to antimicrobials, so that they can be used without causing harm to farmed animals and their handler.