SOUTHERN JOURNAL OF SCIENCES

Due to their diverse properties, plastic materials are used in numerous sectors. It is possible to produce different articles and plastic objects with reduced costs, being more accessible to the population. Conventional plastics are obtained from petroleum-derived raw materials, a non-renewable resource in which their extraction and refining process cause major environmental impacts. The production of plastic reaches a level of approximately one hundred and forty million tons per year, and the disposal of these materials is increasing, generating a high rate of waste and leading to an increase of pollution since the decomposition of these materials lasts about five hundred years old. Conventional plastics can be replaced by bioplastics, a material obtained from renewable raw materials such as potatoes, cassava, maize, and which, when disposed of under favorable conditions, decomposes faster, as during its degradation process at least one step occurs. Through the metabolism of organisms present in the environment. Starch has been widely used in the production of biodegradable packaging, so the objective of this work was to produce a biodegradable bioplastic from the potato starch. Potato starch, glycerin, hydrogen peroxide, distilled water, and commercial agar were used to produce the bioplastic. Bench-scale bioplastics had good organoleptic characteristics, similar in appearance to a conventional plastic obtained from petroleum. The thickness, moisture content, and solubility of the bioplastics were analyzed, as well as their fruit preservation capacity. The samples produced were rigid and with good resistance.

Background: Infectious diseases are a global problem, the second human cause of death. Infectious diseases caused by pathogenic bacteria have been treated with a high degree of efficacy. However, even when the 20th century was considered the “golden age” of antibiotics, bacteria developed a different resistance mechanism to antibiotics. In 2017, the WHO issued an alert about 12 bacteria with an urgent need to develop new antibiotics. Aims: The aim of the present review is to analyze the current knowledge of the antibacterial activity of natural extract-based treatments against the pathogens listed by WHO. Methods: A systematic review of the literature in PubMed was performed to search for publications describing the use of natural extracts as antibiotics over bacteria. We focused on the Gram-Negative group. The exclusion criteria consisted of limiting papers on natural extracts tested over the bacteria culture related to eight selected bacteria, according to an alert issued by WHO in 2017, and seven plant extracts. Results: All the Gram-Negative bacteria listed in 2017 by WHO have been treated, with different degrees of advance, with some of the plant extracts and plant-based compounds reviewed. In general, the first approach is using inhibition disks applied over the bacterial biofilm in solid culture media. Discussion: While Salmonellae and P. aeruginosa have been extensively studied, over N. gonorrhoeae, A. baumannii have been tested with fewer natural extracts. Edible herbs are more often used, as well as artemisa and wine byproducts. In all cases, they are in the early stages of study, not being tested in patients at present. Conclusions: Plant extracts and plant-based compounds are effective as antibacterial, with minimal effects on the host cell. Furthermore, they are sustainable, environmentally friendly, and renewable.

Background: Researchers are carried out to assess rocks containing potassium as an alternative source of fertilizers. These studies are important in reducing the external dependence of Brazil on this commodity. Phonolite is a rock of volcanic origin that has in its mineralogical composition the predominance of feldspar and has been potential to use as an alternative potassium source. The studied rock has 6% total-K but is unavailable to plants in natural rock. Aim: This project evaluated the effect of mechanical activation, wet and dry, on K availability for extractors different and its K leaching curves of phonolite from Poços de Caldas, MG, Brazil. Methods: Phonolite rock was subjected to mechanical activation for 30 and 60 min by wet and dry processes. Particle size distribution, XRD, and FTIR analyses characterized phonolite activated. These results were compared to the behavior of the rock with no activation. K availability (total; water-soluble; exchangeable, non-exchangeable, and structural) was determined in samples activated and no activation. K leaching curves were obtained by successive extractions with 0.01 mol L-1 citric acid and Mehlich-1 solutions to 1812 h and analyzed by FAAS. Results: The samples mechanical activation promoted a reduction in the intensity of the diffraction peaks. In the sample dry mechanical activation for 60 min, K released increased by 15% in relation to the no activation sample. K leaching curves were observed with similar behavior for the extractors and higher K availability after 235 h of total contact time. Discussion: Mechanical activation promoted a decrease in structural K and an increase in non-exchangeable K, released into the soil solution in the medium term. Since the mineralogical composition was not changed, the process action is more efficient in creating the structural defects suggested. K leaching curves corroborate these results, with a continuous and slow K released for a longer contact time. Conclusions: It was concluded that the phonolite activated by dry mechanical activation for 60 min increased K-released content compared with the wet process and ratified the possibility of the activated phonolite rock as a slow-release fertilizer.