The continuous increase of plastic production and mismanagement of the plastic waste have led to a tremendous increase of plastic in the environment. Both, decomposition of larger plastic waste and targeted production of micro-sized particles generates microplastic particles (MP). Microplastics are plastic particles whose size is smaller than 5 mm. Microplastics can be a carrier of various toxins such as additives from industrial manufacturing processes or heavy metals. These toxins can affect entire ecosystem. Due to the harmful effect, MP needs to be removed from the environment. The possibilities of microplastics degradation using bacteria from the environment, that have properties which could degradate microplastics, are being explored. In this paper, biodegradation of two types of the microplastics was conducted, polystyrene (PS) and low density polyethylene (LDPE), with Bacillus cereus, Bacillus subtilis and mixed bacterial culture Pseudomonas alcaligenes and Bacillus sp.. Duration of the experiment was 22 days at 160 rpm, T = ±25 °C, particle size of 300 - 500 μm and concentration of 100 mg/L. Changes in optical density (OD), bacterial colony forming unit (CFU), oxygen concetration, temperature, pH – value, electrical conductivity, total organic carbon (TOC), inorganic carbon (IC) and total carbon (TC) were monitored for 22 days. Variations in anion and cation concentrations were monitored as well. At the beginning and the end of the experiment, LDPE and PS were characterized by infrared spectroscopy with Fourier transformations (FTIR-ATR). According to the results, temperature, pH – value and electrical conductivity have not alternated during the experiment. Bacterial cultures that were used have effectively degraded PS and LDPE over 22 days. Biodegradation is proven by higher decrease of dissolved oxygen concentration in samples with MP, higher bacterial CFU number and formation of inorganic carbon (CO2). FTIR spectrums before and after biodegradation were compared and they show the formation of new groups, reduction of peak intensities and shift of peaks towards the smaller wavelengths. Furthermore, B. cereus and Ps. alcaligenes + Bacillus sp. are better at degradation of PS whilst B. subtilis is better at degradation of LDPE. The results of the performed analysis show that the mixed bacterial culture of Ps. alcaligenes and Bacillus sp. is the best for degradation of both types of microplastics.