Nestor David Ortega-De la Rosa

The valorization of lignocellulosic residues through xylooligosaccharides (XOS) production offers a promising route for obtaining value-added compounds from underutilized biomass. In this study, five biocatalysts were produced by solid-state fermentation using water hyacinth (WH) as the substrate and solid support for five fungal strains. Xylanases were extracted from each fermented solid, exhibiting maximum activity between 45–55 °C and pH 5–7. Additionally, the recovery of hemicellulosic fractions from WH and sugarcane bagasse (SCB) reached 14.3 ± 0.91% and 18.4 ± 0.22% of initial dry biomass, respectively. Commercial xylan and hemicellulosic fractions from WH (WHh) and SCB (SCBh), at an initial concentration of 25 g/L, were partially hydrolyzed, releasing 12–18, 9–12 and 2–4 g/L of reducing sugars, respectively, after 6 h of reaction, depending on the enzyme extract used. Xylobiose was detected in all hydrolysates, with the Trichoderma harzianum extract yielding the highest concentrations: 8.3, 4.4, and 2.4 g/L from xylan, WHh, and SCBh, respectively. Hydrolysates supplemented into MRS medium enhanced the growth of Bifidobacterium lactis and Lactococcus lactis compared to the control medium. These findings demonstrate the feasibility of using waste-derived biocatalysts and WH and SCB as inexpensive and abundant sources of hemicellulose to produce XOS-containing hydrolysates with potential prebiotic applications.

This study aimed to isolate and identify fungi capable of producing xylanases and cellulases. Thirty-eight fungal strains were isolated from decaying water hyacinth (WH), and two were selected based on their superior enzyme production under solid-state fermentation (SSF). The strains were identified through morphological, cultural, and molecular analyses as Aspergillus austwickii B6 and Trichoderma harzianum M7. Their ribosomal ITS sequences were deposited in GenBank under accession numbers PQ142799.1 for A. austwickii B6 and PQ007458.1 for T. harzianum M7. Enzyme production was evaluated under SSF using eight culture medium variants prepared with natural or pretreated biomasses of WH and sugarcane bagasse (SCB), combined with either NaNO₃ or (NH₄)₂SO₄ as nitrogen sources. The maximum xylanase and cellulase activities were 752 and 65 U/g dry matter (DM), respectively, for A. austwickii B6, and 1724 and 152 U/g DM for T. harzianum M7, when cultivated on a low-cost medium composed of pretreated WH, (NH₄)₂SO₄, and a simple mineral salt solution. These findings highlight the potential of locally isolated fungal strains and lignocellulosic residues as cost-effective substrates and inducers of xylanase and cellulase production under SSF and underscore the importance of WH pretreatment to enhance substrate availability and maximize enzyme yields.

Hydrogel particles are essential in biological applications because of their distinctive capacity to retain water and encapsulate active molecules within their three-dimensional structure. Typical particle sizes range from nanometers (10–500 nm) to micrometers (1–500 µm), depending on the specific application and method of preparation. These characteristics render them optimal carriers for the administration of active compounds, facilitating the regulated and prolonged release of pharmaceuticals, including anticancer agents, antibiotics, and therapeutic proteins. Hydrogel particles can exhibit various morphologies, including spherical, rod-shaped, disk-shaped, and core–shell structures. Each shape offers distinct advantages, such as improved circulation time, targeted drug delivery, or enhanced cellular uptake. Additionally, hydrogel particles can be engineered to respond to various stimuli, such as temperature, pH, light, magnetic fields, and biochemical signals. Furthermore, their biocompatibility and capacity to acclimate to many biological conditions make them appropriate for sophisticated applications, including gene treatments, tissue regeneration, and cell therapies. Microfluidics has transformed the creation of hydrogel particles, providing precise control over their dimensions, morphology, and stability. This technique facilitates reproducible and highly efficient production, reducing reagent waste and optimizing drug encapsulation. The integration of microfluidics with hydrogels provides opportunities for the advancement of creative and effective solutions in contemporary medicine.

Only a few halophilic archaea producing carboxylesterases have been reported. The limited research on biocatalytic characteristics of archaeal esterases is primarily due to their very low production in native organisms. A gene encoding carboxylesterase from Halobacterium salinarum NRC-1 was cloned and successfully expressed in Haloferax volcanii. The recombinant carboxylesterase (rHsEst) was purified by affinity chromatography with a yield of 81%, and its molecular weight was estimated by SDS-PAGE (33 kDa). The best kinetic parameters of rHsEst were achieved using p-nitrophenyl valerate as substrate (K_M = 78 µM, k_cat = 0.67 s⁻¹). rHsEst exhibited great stability to most metal ions tested and some solvents (diethyl ether, n-hexane, n-heptane). Purified rHsEst was effectively immobilized using Celite 545. Esterase activities of rHsEst were confirmed by substrate specificity studies. The presence of a serine residue in rHsEst active site was revealed through inhibition with PMSF. The pH for optimal activity of free rHsEst was 8, while for immobilized rHsEst, maximal activity was at a pH range between 8 to 10. Immobilization of rHsEst increased its thermostability, halophilicity and protection against inhibitors such as EDTA, BME and PMSF. Remarkably, immobilized rHsEst was stable and active in NaCl concentrations as high as 5M. These biochemical characteristics of immobilized rHsEst reveal its potential as a biocatalyst for industrial applications.

Acinetobacter species are identified as producing surface-active and emulsifying molecules known as bioemulsifiers. Production, characterization and stability of bioemulsifiers produced by Acinetobacter bouvetii UAM25 were studied. A. bouvetii UAM25 grew in three different carbon and energy sources: ethanol, a glycerol–hexadecane mixture and waste cooking oil in an airlift bioreactor, showing that bioemulsifier production was growth associated. The three purified bioemulsifiers were lipo-heteropolysaccharides of high molecular weight (4866 ± 533 and 462 ± 101 kDa). The best carbon source and energy for bioemulsifier production was wasted cooking oil, with a highest emulsifying capacity (76.2 ± 3.5 EU mg⁻¹) as compared with ethanol (46.6 ± 7.1 EU mg⁻¹) and the glycerol–hexadecane mixture (49.5 ± 4.2 EU mg⁻¹). The three bioemulsifiers in our study displayed similar macromolecular structures, regardless of the nature (hydrophobic or hydrophilic) of the carbon and energy source. Bioemulsifiers did not decrease surface tension, but the emulsifying capacity of all of them was retained under extreme variation in salinity (0–50 g NaCl L⁻¹), pH (3–10) and temperature (25–121 °C), indicative of remarkable stability. These findings contribute to understanding of the relationship between: production, physical properties, chemical composition and stability of bioemulsifiers for their potential applications in biotechnology, such as bioremediation of hydrocarbon-contaminated soil and water.