Indian Institute of Science Education and Research, Mohali

The conversion of polyethylene (PE) into photo-responsive carbon dots (CDs) has emerged as a promising waste plastic mitigating approach by upcycling it into value-added materials.However, this single-step approach for charring of polyethylene (PE) with concentrated H₂SO₄ followed by in-situ oxidation into CDs limits the reutilization of H₂SO₄ due to unavoidable dilutionTherefore, we here introduce a two-step approach, wherein char is produced from PE first, separated, and then oxidized to obtain CDs.This way, we could reuse the acid for up to seven cycles.The CDs obtained thus bear similarity up to the third cycle but gradually change thereafter, exhibiting variations in aromatic and amorphous carbon contents, surface functional moieties, and O₂ harvesting capabilities.During reutilization, the charring ability of H₂SO₄ gradually reduces due to its reaction with PE and becomes ineffective after the 7th cycle.To validate the industry feasibility, we scaled up CD preparation from 1 g to 50 g, and found their properties comparable.Further, we have developed a strategy to purify the residual acid of carbon impurities for downstream use after the 7th cycle.Finally, we utilized the CDs′ O₂ harvesting and photocatalytic abilities to convert benzyl-alcs. into corresponding aldehydes in ambient air.

A novel l-rhamnose isomerase was identified and cloned from an extreme-temperature aquatic habitat metagenome. The deduced amino acid sequence homology suggested the possible source of this metagenomic sequence to be Chloroflexus islandicus. The gene expression was performed in a heterologous host, Escherichia coli, and the recombinant protein l-rhamnose isomerase (L-RIM) was extracted and purified. The catalytic function of L-RIM was characterized for d-allulose to d-allose bioconversion. d-Allose is a sweet, rare sugar molecule with anti-tumour, anti-hypertensive, cryoprotective, and antioxidative properties. The characterization experiments showed L-RIM to be a Co++- or Mn++-dependent metalloenzyme. L-RIM was remarkably active (~ 80%) in a broad spectrum of pH (6.0 to 9.0) and temperature (70 to 80 °C) ranges. Optimal L-RIM activity with d-allulose as the substrate occurred at pH 7.0 and 75 °C. The enzyme was found to be excessively heat stable, displaying a half-life of about 12 days and 5 days at 65 °C and 70 °C, respectively. L-RIM catalysis conducted at slightly acidic pH of 6.0 and 70 °C achieved biosynthesis of about 30 g L−1 from 100 g L−1d-allulose in 3 h.

• The present study explored an extreme temperature metagenome to identify a novel gene that encodes a thermostable l-rhamnose isomerase (L-RIM)• L-RIMexhibits substantial (80% or more) activity in a broad spectrum of pH (6.0 to 9.0) and temperature (70 to 80 °C) ranges• L-RIMis excessively heat stable, displaying a half-life of about 12 days and 5 days at 65 °C and 70 °C, respectively

Corneal disease is a major cause of blindness. Transplantation of cadaver-derived corneas (keratoplasty) is still the current therapy of choice; however, the global shortage of donor corneas continues to drive a search for alternatives. To this end, biosynthetic corneal substitutes have recently begun to gain importance. Here, we present a novel method for the generation of a cornea-like tissue (CLT), using corneo-scleral rims discarded after keratoplasty.

Type I collagen was polymerized within the corneo-scleral rim, which functioned as a 'host' mould, directing the 'guest' collagen to polymerize into disc-shaped cornea-like material (CLM), displaying the shape, curvature, thickness, and transparency of normal cornea. This polymerization of collagen appears to derive from some morphogenetic influence exerted by the corneo-scleral rim. Once the CLM had formed naturally, we used collagen crosslinking to fortify it, and then introduced cells to generate a stratified epithelial layer to create cornea-like tissue (CLT) displaying characteristics of native cornea. Through the excision and reuse of rims, each rim turned out to be useful for the generation of multiple cornea-shaped CLTs.

The approach effectively helps to shorten the gap between demand and supply of CLMs/CLTs for transplantation. We are exploring the surgical transplantation of this CLT into animal eyes, as keratoprostheses, as a precursor to future applications involving human eyes. It is possible to use either the CLM or CLT, for patients with varying corneal blinding diseases.