Production of functional human galectin-1 in transplastomic tobacco and simplified recovery via batch-mode purification

Plant molecular farming has established itself as a transformative technology for the cost-effective and sustainable production of biopharmaceuticals, offering scalable solutions to meet growing global demand. Among the different stable plant expression systems, plastid-based platforms are particularly attractive due to their high recombinant protein accumulation potential, genetic stability, and reduced risk of transgene escape. Human Galectin-1 (hGAL1) is a β-galactoside-binding lectin with potent immunomodulatory properties, positioning it as a promising therapeutic candidate for autoimmune and inflammatory diseases. Preserving its native conformation and carbohydrate-binding capacity is essential to keep its biological activity, and both properties may be compromised under suboptimal expression or purification conditions. Here, we demonstrate the relevance of chloroplast transformation in <i>Nicotiana tabacum</i> as a platform for producing functional hGAL1, which accumulated up to 5.67 mg per kg of leaf tissue, corresponding to ~0.05% of total soluble protein (TSP). Using a simplified batch-mode purification strategy, intact hGAL1 retaining carbohydrate-binding activity was obtained and functional properties as shown by its ability to induce T cell apoptosis in a dose-dependent manner. These results highlight the potential of a transplastomic tobacco platform to deliver biologically active human lectins with therapeutic relevance, while minimizing downstream processing complexity, supporting their use in cost-effective biopharmaceutical production.