Antibiotics are low molecular-weight molecules produced as secondary metabolites, mainly by microorganisms that live in the soil. Microbial secondary metabolites have been a major source of clinically useful antibiotics. Members of the genus Bacillus are known to produce a wide arsenal of antimicrobial substances, including peptide and lipopeptide antibiotics. These peptides can be classified into two different groups based on whether they are ribosomally (bacteriocins) or nonribosomally (polymyxins and iturins) synthesized. The present paper provides a general overview of antimicrobial peptides derived from Bacillus species, including their structure and classification, as well as several extraction and purification methods used to obtain these bioactive compounds.

This review paper aims to summarize aspects related to the biotechnological potential of halophile and halotolerant microbes in the sustainable management of agricultural practices. During the past few years, different microorganisms have been isolated from saline environments (including in Romania) and characterized for the discovery of new species and their potential use in industrial applications. This paper presents a brief literature review, conducted using various open access scientific databases using keywords such as halophilic bacteria/bioinoculants, saline soils, halotolerant ecology, novel halophiles, plant growth-promoting halophiles, salinity stress, salt-tolerant microbes, etc.

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Biotechnology, molecular biology and genetic engineering, and bioprospecting play a crucial role in our common future, enabling industrially important microorganisms to ensure sustainable products (fuels, chemicals, pharmaceuticals, food, drug delivery systems, medical devices etc.) and new bioeconomic opportunities. Biotechnological applications are able to provide cost-effective green alternatives to conventional industrial processes, which are currently affecting the nature and biodiversity. Klebsiella species are among the well-studied microbes both in medicine field, as ones of the most resilient opportunistic pathogens, and in industry, due to their promising biochemical properties, and their potential as better hosts than other microorganisms, for i.e. in genetic manipulation. Klebsiella oxytoca and Klebsiella pneumoniae are ubiquitously found in natural environments, but also as commensals in the human gut, and associated with a high-resistance to the first-line antibiotics. However, these specific strains are continuously isolated and studied for different industrial purposes (i.e. bulk chemicals and biofuels production, medical diagnosis, nanoparticles and exopolysaccharides synthesis, plant growth promoting activities, bioremediation and biodegradation agents etc.), and scientific results regarding their biotechnological potential could generate big impact for global bioeconomy development. Recently, research in synthetic biology gained a lot of attention, and new techniques highlight ways to reprogramme these microbial cells in view of high-yield or high-quality new chemicals obtainment. Therefore, some scientific research niches are emerging in biotechnology, and unknown metabolic pathways and genes are identified and further studied, to provide alternative solutions to the global challenges.

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The present work aimed to investigate the efficiency of kinetic modeling and Response Surface Methodology (RSM), by employing a Central Composite Rotatable Design (CCRD) and to evaluate the effects of carbon and nitrogen sources, inoculation volume, and bioprocess time on an exopolysaccharide (EPS) producer, Klebsiella oxytoca ICCF 419, in batch fermentation with shaken flasks. Among the kinetic models tested, logistic equations were found to fit accordingly, with a correlation coefficient (R2 ) of 0.999. The interaction between glucose and corn steep liquor was found to have a significant impact on the EPS production, and glucose (2% w/v), and a 5% v/v inoculum of 24 hours age, are sufficiently to positively affect the bioprocess, if it is desired only a maximum cell growth, but not associated with the polymer synthesis. The optimal formula predicted by the RSM design was experimentally validated by the following results: 12.16 g EPS/L and 1.65 dry biomass/L, after 48 hours fermentation.

The objective of this work was to optimize the bioprocess parameters, using Klebsiella oxytoca ICCF 419 to obtain an exopolysaccharide based on lactose as substrate. A kinetic study was employed and Logistic and Gompertz models were applied to describe the polysaccharide production, in relation with biomass growth and substrate consumption. The RSM methodology based on Central Composite Rotatable Design was used to evaluate and optimize the effect of lactose, corn extract, KH2PO4 and citric acid concentrations as independent variables on the polysaccharide production, biomass growth and substrate consumption as the response functions. The interaction effects and optimal parameters were obtained using Design Expert Software (version 9.0.6.2). The significance of the variables and their interactions was tested by means of ANOVA analysis with a 99% confidence level. The optimum culture conditions were determined and the model prediction was compared with experimental results. At an initial value of 23.45 for the C/N in the fermentation medium, the strain produces 17.41 g/L of crude polysaccharide and 2.53 g/L dry biomass. The EPS production was significantly influenced by lactose, corn extract and KH2PO4, while the citric acid had no influence. The biomass growth was influenced by the corn extract, KH2PO4 and citric acid.