Initial biophysical characterization of Amynthas gracilis giant extracellular hemoglobin (HbAg)

Biorecognition of hydrogen peroxide using a novel electrochemical platform designed with Glossoscolex paulistus giant hemoglobin

The giant extracellular hemoglobin of the annelid Glossoscolex paulistus (HbGp; 3.6 MDa) is a valuable and underexplored supramolecular hemoprotein system for the biorecognition of reactive oxygen species. In this work, an efficient and simple electrochemical platform was designed for analyzing H₂O₂, using HbGp covalently immobilized on Nafion®-modified glassy carbon electrode, named as HbGp/Nafion/GCE. Voltammetric and spectroscopic studies revealed the importance of prior modification of the electrodic support with the conducting polymer to obtain satisfactory hemoglobin electroactivity, as well as a biocompatible microenvironment for its immobilization. In terms of biological activity, it was observed a greater reactivity of the biomolecule in acidic medium, enabling the detection of the analyte by a quasi-reversible mechanism, whose kinetics was limited by analyte diffusion. In the presence of H₂O₂, the native structure of hemoglobin (oxy-HbGp (Fe²⁺)) oxidizes to ferryl-HbGp (Fe⁴⁺) and this redox reaction can be monitored on HbGp/Nafion/GCE with a detection limit of 8.5 × 10^‒7  mol L^-1. In addition to high sensitivity, the electrochemical biosensor also provided reproducible, consistent, and accurate measurements. The electroanalytical method showed an appropriate performance to quantify different levels of H₂O₂ in milk samples, proving the potential of HbGp/Nafion/GCE for this purpose.

Repurposing fish waste into gelatin as a potential alternative for mammalian sources: A review

Mammalian gelatin is extensively utilized in the food industry because of its physicochemical properties. However, its usage is restricted and essentially prohibited for religious people. Fish gelatin is a promising alternative with no religious and social restrictions. The desirable properties of fish gelatin can be significantly improved by various methods, such as the addition of active compounds, enzymes, and natural crosslinking agents (e.g., plant phenolics and genipin), and nonthermal physical treatments (e.g., ionizing radiation and high pressure). The aim of this study was to explore whether the properties of fish gelatin (gel strength, melting or gelling temperature, odor, viscosity, sensory properties, film-forming ability, etc.) could be improved to make it comparable to mammalian gelatin. The structure and properties of gelatins obtained from mammalian and fish sources are summarized. Moreover, the modification methods used to ameliorate the properties of fish gelatin, including rheological (gelling temperature from 13-19°C to 23-25°C), physicochemical (gel strengths from ∼200 to 250 g), and thermal properties (melting points from ∼25 to 30°C), are comprehensively discussed. The relevant literature reviewed and the technological advancements in the industry can propel the development of fish gelatin as a potential alternative to mammalian gelatin, thereby expanding its competitive market share with increasing utility.