Víctor Manuel Luna Pabello

Studies performed in Valle de Bravo (VB) reservoir in Mexico record the presence of cyanobacteria proliferation and microcystin LR (MC-LR), both from 1998 to 2022, related mainly to two environmental factors; first, nitrates (NO ₃ ) and second, temperature. We statistically analyzed data from nine selected works in VB and found that these parameters do not converge seasonally during stratification and mixing. We propose that cyanobacteria, being photoautotrophic organisms, their proliferation and toxin-producing capacity are mainly determined by the amount of photosynthetically active radiation (PAR) rather than NO ₃ . We conducted experimental tests to evaluate the toxic wild cyanobacterium, Microcystis aeruginosa , producer of microcystin LR (MC-LR), exposed to 100 µmol photons m ⁻² s ⁻¹ of PAR and three fractions at different descending concentrations of NO ₃ . The results of the analyses on data from nine studies showed that cyanobacteria did not proliferate due to the seasonal availability of NO ₃ but rather due to temperature. In vitro, we observed that increased PAR had an effect on the growth of M. aeruginosa . The presence of MC-LR was driven by the inverse relationship between PAR and NO ₃ . Therefore, we conclude that adding PAR monitoring to studies of tropical monomictic systems would contribute to expanding our understanding of NO ₃ and temperature-related effects on the proliferation of cyanobacteria and their toxins.

The rapid expansion of shrimp aquaculture has led to the generation of nutrient-rich effluents, which contribute to environmental degradation if inadequately managed. This study evaluated the potential of Dunaliella salina for the reuse of shrimp aquaculture wastewater (SAW) in biofloc production systems under varying dilution levels (0%, 25%, and 50%) and the simultaneous production of high-value biomass. Growth kinetics were modeled using a four-parameter logistic model, and nutrient removal, biochemical composition, and fatty acid profile were assessed. D. salina exhibited substantial growth in undiluted SAW, achieving over 80% removal of total nitrogen and reducing the organic load, as measured by a chemical oxygen demand reduction of more than 79%. In SAW treatments, the protein content ranged from 24.7% to 26.3%, while the lipid content reached up to 67.1% in a 25% SAW dilution. Chlorophyll a and total carotenoids were measured at 5.3–7 µg/mL and 4.1–5.7 µg/mL, respectively, in SAW treatments. The polyunsaturated fatty acid content in undiluted SAW was 34.5%, with α-linolenic acid (C18:3n3) and linoleic acid (C18:2n6) comprising 12% and 7.5%, respectively. This study demonstrates the ability of D. salina to valorize shrimp aquaculture wastewater in biofloc systems into lipid-rich, bioactive biomass, supporting its use in integrated aquaculture biotechnology systems for sustainable wastewater management and bioproduct generation.

Plastic is used excessively due to its excellent properties and its low cost. This has led to the ubiquitous accumulation of waste as it takes a very long time to biodegrade. Until now, several research projects have developed different biodegradable plastics, and the tests to validate them are still being undertaken. In this research, a biodegradability test was performed on a bioplastic synthesized from tamarind xyloglucan and ethyl acrylate (b-XgT), designed to be a substitute for polystyrene. A sample of the b-XgT was composted in laboratory conditions and CO2 release measurements were made. The results showed a biodegradation time of 18 days with a loss of mass of 40.3% and a final pH of 7.1. The b-XgT was found to be biodegradable of the compostable type through the anaerobic route, which promotes the digestion of compounds such as xylose that contribute to the degradation of the whole polymer.

Los plásticos han sido motivo de atención debido a su desmedido uso y acumulación como residuo en los últimos 20 años al ser desechos no biodegradables, por lo cual, los bioplásticos se posicionan como sustitutos alternativos pertinentes por su fácil asimilación por los microoganismos. El objetivo de este estudio fue caracterizar los microorganismos que participaron en la biodegradación de un bioplástico de acrilato de etilo (AE) y xiloglucano de tamarindo (XgT), durante una prueba de biodegradabilidad realizada a través de biorreactores de compostaje, para a su vez reconocer la viabilidad de desarrollo microbiano en tales sistemas de degradación. Para ello, se realizó la siembra primaria en agar sangre y Sabouraud, la siembra secundaria en BHI, medio en el que se diferenciaron 16 morfologías coloniales, con tendencia a bacilos Gram (+); se hizo el perfil enzimático en agar almidón (AA), agar de leche descremada (LD) y agar Baird-Parker (BP) para evidenciar la participación de enzimas amilasa, caseinasa y lecitinasa; asimismo se hizo el análisis cualitativo de degradación y el recuento en placa, el cual mostró un promedio de 2,15 x 1012 UFC/ mL de muestra, exhibiendo condiciones para la viabilidad microbiana en los biorreactores de compostaje.

La investigación se enfocó en la determinación del contenido proteico y nutracéutico en el ciliado de vida libre Paramecium aurelia, que fue aislado de una fuente silvestre y se identi có. Los cultivos axénicos de P. aurelia se realizaron en un bio-reactor automatizado con control de pH a 7.0, 28 ◦C, oxígeno disuelto superior a 2 mg L^-1 y agitación a 70 rpm por 72 h. El medio de cultivo se integró con 700 mL de infusión de lechuga y trigo, diluidos en 1 L de agua destilada e inóculo de 300 mL con 3 x 103 células mL^-1. De estos cultivos se obtuvieron 74.1 mg L^-1 de biomasa seca, 48.6 % de proteínas y 37.6 % de lípidos, conformados principalmente por ácidos grasos: oleico (20.8 %), linoleico (11.1 %), gama-linolénico (3.6 %) y araquidónico (6.0 %). Las vitaminas presentes fueron: A (retinol, 81.27 μg g^-1), E (tocoferol, 28.73 mg g^-1) y D3 (colecalciferol, 4.49 mg g^-1). La biomasa de P. aurelia, podría constituir una fuente importante de proteína y de sustancias nutracéuticas.