Karst spring microbiome: Diversity, core taxa, and community response to pathogens and antibiotic resistance gene contamination.

Karst aquifers are important water resources for drinking water supplies worldwide. Although they are susceptible to anthropogenic contamination due to their high permeability, there is a lack of detailed knowledge on the stable core microbiome and how contamination may affect these communities. In this study, eight karst springs (distributed across three different regions in Romania) were sampled seasonally for one year. The core microbiota was analysed by 16S rRNA gene amplicon sequencing. To identify bacteria carrying antibiotic resistance genes and mobile genetic elements, an innovative method was applied, consisting of high-throughput antibiotic resistance gene quantification performed on potential pathogen colonies cultivated on Compact Dry™ plates. A taxonomically stable bacterial community consisting of Pseudomonadota, Bacteroidota, and Actinomycetota was revealed. Core analysis reaffirmed these results and revealed primarily freshwater-dwelling, psychrophilic/psychrotolerant species affiliated to Rhodoferax, Flavobacterium, and Pseudomonas genera. Both sequencing and cultivation methods indicated that more than half of the springs were contaminated with faecal bacteria and pathogens. These samples contained high levels of sulfonamide, macrolide, lincosamide and streptogramins B, and trimethoprim resistance genes spread primarily by transposase and insertion sequences. Differential abundance analysis found Synergistota, Mycoplasmatota, and Chlamydiota as suitable candidates for pollution monitoring in karst springs. This is the first study highlighting the applicability of a combined approach based on high-throughput SmartChip™ antibiotic resistance gene quantification and Compact Dry™ pathogen cultivation for estimating microbial contaminants in karst springs and other challenging low biomass environments.

L-Poly(lactic acid) Production by Microwave Irradiation of Lactic Acid Obtained from Lignocellulosic Wastes.

L-polylactic acid (PLA), a semi-crystalline aliphatic polyester, is one of the most manufactured biodegradable plastics worldwide. The objective of the study was to obtain L-polylactic acid (PLA) from lignocellulosic plum biomass. Initially, the biomass was processed via pressurized hot water pretreatment at a temperature of 180 °C for 30 min at 10 MPa for carbohydrate separation. Cellulase and the beta-glucosidase enzymes were then added, and the mixture was fermented with Lacticaseibacillus rhamnosus ATCC 7469. The resulting lactic acid was concentrated and purified after ammonium sulphate and n-butanol extraction. The productivity of L-lactic acid was 2.04 ± 0.18 g/L/h. Then, the PLA was synthesized in two stages. Firstly, lactic acid was subjected to azeotropic dehydration at 140 °C for 24 h in the presence of xylene, using SnCl2 (0.4 wt.%) as a catalyst, resulting in lactide (CPLA). Secondly, microwave-assisted polymerization was carried out at 140 °C for 30 min with 0.4 wt.% SnCl2. The resulting powder was purified with methanol to produce PLA with 92.1% yield. The obtained PLA was confirmed using electrospray ionization mass spectrometry, nuclear magnetic resonance, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. Overall, the resulting PLA can successfully replace the traditional synthetic polymers used in the packaging industry.

Optimization of Lipid Extraction from Spirulina spp. by Ultrasound Application and Mechanical Stirring Using the Taguchi Method of Experimental Design.

The present study uses the Taguchi method of experimental design to optimize lipid extraction from Spirulina spp. by ultrasound application and mechanical stirring. A Taguchi L9 orthogonal array was used to optimize various parameters, such as methanol: chloroform (M:C) ratio, biomass: solvent ratio, and extraction time for lipid extraction. The results were analyzed using the signal-to-noise (S/N) ratio and analysis of variance (ANOVA). The biomass: solvent ratio significantly influenced lipid content (p < 0.05) with 92.1% and 92.3% contributions to the lipid and S/N ratio data, respectively. The extraction time presented a contribution value of 5.0%, while the M:C ratio presented the most negligible contribution of 0.4% for S/N data. The optimum extraction conditions were: M:C ratio of 1:1, biomass: solvent ratio of 1:60, and extraction time of 30 min. The predominant fatty acids were palmitic acid (44.5%), linoleic acid (14.9%), and gamma-linolenic acid (13.4%). The confirmation experiments indicated a lipid content of 8.7%, within a 95% confidence interval, proving the Taguchi method's effectiveness in optimizing the process parameters for lipid extraction.

Zeolites Reduce the Transfer of Potentially Toxic Elements from Soil to Leafy Vegetables.

The ability of natural zeolite amendment to reduce the uptake of potentially toxic elements (PTEs) by lettuce, spinach and parsley was evaluated using pot experiments. PTE concentrations in roots and shoots, as well as the pseudo total (PT), water soluble (WS) and bioavailable (BA) PTE fractions in the amended soils, were assessed. Although the PT PTE concentration was high, the WS fraction was very low (<0.4%), while the BA fraction varied widely (<5% for Cr, Mn and Co, <15% for Ni, Pb and Zn, >20% for Cd and Cu). PTE concentration decreased in both roots and shoots of all leafy vegetables grown on zeolite amended soils, especially at high amendment dose (10%). The uptake of PTEs mainly depended on plant species, PTE type and amendment dose. With the exception of Zn in spinach, the bioaccumulation factor for roots was higher than for shoots. Generally, lettuce displayed the highest PTE bioaccumulation capacity, followed by spinach and parsley. Except for Zn in spinach, the transfer factors were below 1 for all PTEs, all plant species and all amendment doses. Our results showed that the natural zeolites are promising candidates in the reclamation of contaminated soils due to their ability to immobilize PTEs.

Exploring the Properties of Micronized Natural Zeolitic Volcanic Tuff as Cosmetic Ingredient.

This study explores the characteristics of a micronized natural zeolitic volcanic tuff (MZ) as ingredient in cosmetic formulations. In particular, the purpose was to prepare and investigate the organoleptic and physicochemical properties of two representative cosmetic formulations containing MZ. The MZ samples were characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. pH, cation exchange capacity (CEC), apparent density, chemical composition and particle size distribution of MZ samples were also determined. The micronization treatment applied did not produce significant structural and physicochemical changes with respect to the raw zeolitic volcanic tuff. The prepared formulations containing 5% MZ with different particle sizes (100-125 µm and 125-250 µm) were subjected to preliminary and accelerated stability tests, and the pH and organoleptic properties were also evaluated. The cosmetic formulations presented a pH of 4.3, a pleasant touch, good spreadability, easy application on skin, no color alteration and a good stability after 15, 30 and 60 days of storage at room temperature, low temperature and freezer during the accelerated stability tests. The obtained results endorse the MZ as suitable for the development of formulations exploiting the clinoptilolite properties as a cosmetic ingredient.