Soil microorganisms play an important role in maintaining natural ecological balance through active participation in carbon, nitrogen, sulfur, and phosphorous cycles. Phosphate-solubilizing bacteria (PSB) are of high importance in the rhizosphere, enhancing the solubilization of inorganic phosphorus complexes into soluble forms available for plant nutrition. The investigation of this species of bacteria is of major interest in agriculture, as they can be used as biofertilizers for crops. In the present study, 28 isolates of PSB were obtained after the phosphate enrichment of soil samples from five Tunisian regions. Five PSB species were identified by 16S rRNA gene sequencing including Pseudomonas fluorescens, P. putida, and P. taiwanensis, Stenotrophomonas maltophilia, and Pantoea agglomerans. Solid and liquid Pikovskaya’s (PVK) and National Botanical Research Institute’s (NBRIP) media containing insoluble tricalcium phosphate were used for the evaluation of the phosphate solubilization ability of the bacterial isolates by two methods: visual evaluation of the solubilization zone around colonies (halo) and determination of solubilized phosphates in liquid medium by the colorimetric method of the vanado-molybdate yellow. Based on the results of the halo method, the isolate of each species that showed the higher phosphate solubilization index was selected for evaluation of phosphate solubilization by the colorimetric method. In the liquid media, the bacterial isolates showed phosphate solubilization ranging from 535.70 to 618.57 µg mL⁻¹ in the NBRIP medium, and 374.20 to 544.28 µg mL⁻¹ in the PVK medium, with the highest values produced by P. fluorescens. The best phosphate solubilization ability and higher reduction in broth pH, which indicates higher organic acid production, were achieved in NBRIP broth for most of the PSB. Strong correlations were observed between the average capability of PSB to solubilize phosphates and both the pH and total phosphorous content in the soil. The production of the hormone indole acetic acid (IAA), which can promote plant growth, was observed for all five PSB species. Among them, P. fluorescens obtained from the forest soil of northern Tunisia showed the highest production of IAA (50.4 ± 0.9 µg mL⁻¹).

This paper aims to present an interdisciplinary approach intended to raise awareness for Sustainable Development Goals in the context of STEM (Science, Technology, Engineering, and Mathematics) hands-on activities targeted to elementary and secondary school. In particular, contents related to the physics of sound are used to warn about the dangers of noise pollution and its consequences for health, well-being, and productivity. Therefore, it is crucial to inform and raise community awareness on this issue, as well as on the measures needed to prevent its consequences. This research is inserted in a broader pedagogical project that includes primary school and secondary school teachers’ professional development and visits to schools to perform several hands-on activities in class aiming to provide students with 21st-century skills related to STEM education. Based on the literature, questionnaires, and participant observation, an empirical study was conducted with teachers who participated in a professional development programme. It is concluded that teachers and students understood the dangers of noise pollution and the measures to be taken to prevent them. Therefore, higher education institutions have a crucial role in the community, namely, through partnerships with schools and teachers’ training centres to raise awareness and disseminate and increase Sustainable Development practices in the community.

Purpose The purpose of this paper is to describe the case of the Valorbio research project, in which students of different high-level programs were involved in the experimental work and in the dissemination of results in collaboration with the research team. Design/methodology/approach The inclusion in higher education curricula of content related to the sustainable development should be a preferred mechanism for the dissemination of good practices of sustainability. Another equally important way to achieve this is to involve students in research projects that seek solutions to the societal challenges related to sustainable growth. The Valorbio project aims to meet the needs for treating and reusing wastewater and solid waste. Its main goal was the development of modular systems for wastewater treatment based on constructed wetlands, exploring the possibility of the treatment systems being composed of solid waste and by-products from significant industrial sectors. Findings The students' contribution to the research work was relevant and simultaneously allowed them to acquire skills on sustainable development. Additionally, the students contributed to the dissemination of the results. The Valorbio project can thus be considered a successful application of the concept of project-based learning (PBL), as a way to include sustainability issues content in the higher education curricula. Originality/value The applied experimental work had an original approach regarding the equipment design, the waste materials valuation, as well as the integration of waste treatment processes in the circular economy paradigm. This paper is the first reported PBL experience involving students of short-cycle technical-professional programs in partnership with first and second-level students and a research team.