Zhejiang University of Technology

5-Aminolevulinic acid (5-ALA) is a basic precursor in the bioproduction of tetrapyrrole compounds, such as heme, chlorophyll, and vitamin B₁₂. Its extensive applications in agriculture, medicine, cosmetics and animal feed industry have garnered substantial attention. In agriculture, 5-ALA works as an effective plant growth regulator, improving crop yield, stress tolerance, and product quality. Nonetheless, old chemical production of 5-ALA faces challenges because of complex reaction pathways, low productivity, and environmental concerns. This has directed towards a rising interest in sustainable microbial production approaches. Latest developments in metabolic engineering and synthetic biology have assisted the development of effective bacterial cell factories for 5-ALA bioproduction. Key approaches comprise optimizing precursor supply and cofactor regeneration, reworking inborn C4 and C5 biosynthetic pathways, classifying and alleviating rate-limiting enzymes, engineering transport systems for 5-ALA secretion, decreasing competing pathways, and reducing by-product formation. Furthermore, the addition of biosensor-based vigorous regulation and systems-level metabolic control has considerably boosted production robustness and yield. These technical novelties have accelerated the evolution of microbial 5-ALA production from the laboratory to industrial uses. This review offers a comprehensive overview of recent advancements in bacterial 5-ALA bioproduction, focusing on host selection, pathway engineering strategies, regulatory mechanisms, and evolving biotechnological applications. Lastly, it discusses present challenges and future perspectives to guide the development of next-generation microbial platforms for competent and sustainable 5-ALA synthesis.

The structural and functional modification of natural polysaccharides is a key research area in the food and pharmaceutical sectors. However, traditional modification techniques suffer from limitations such as low efficiency and significant pollution. As the demand for efficient and environmentally friendly polysaccharide modification methods grows, cold plasma, an emerging, eco-friendly, and non-thermal treatment technology, offers a highly promising strategy for altering the structural and functional properties of polysaccharides. This review provides an in-depth overview of the latest advances in the cold plasma modification of natural polysaccharides. It elucidates the generation methods, mechanisms, and regulatory factors of this technology, while analyzing its effects on the structure, physicochemical properties, and biological activities of polysaccharides, such as antioxidant, antidiabetic, and immunomodulatory effects. The application of plasma-activated water is also introduced, and the challenges associated with industrialization and future directions are discussed. This review provides theoretical support for the high-value utilization of polysaccharides.

Microfibers (MFs) are a prevalent form of microplastics in aquatic environments and are frequently ingested by aquatic organisms. In nature, individual fibers do not always remain straight but can bend, coil, or become partially self-entangled, potentially altering their biological interactions. However, how such morphological variability influences MF ingestion by benthic gastropods remains poorly understood. Here, we exposed the freshwater snail Sinotaia quadrata to 50 items/L, within the range reported for freshwater systems, of polyethylene terephthalate and polyamide MFs, including elongated single fibers and coiled forms derived from the same individual fibers of corresponding lengths but exhibiting smaller external dimensions. Regardless of food availability and across all tested size classes, snails ingested significantly more elongated single fibers than coiled MFs. Ingestion of both forms peaked within 6 h; however, elongated fibers exhibited longer retention times in the digestive tract, whereas coiled forms were largely egested within 24 h. Microscopic observations indicated that radula-mediated feeding interactions more effectively captured elongated, flexible fibers, whereas coiled MFs were more likely to undergo transient contact without sustained retention and be dislodged during repeated radula-mediated movements. Scanning electron microscopy and micro-Raman analyses further revealed localized surface irregularities on ingested fibers. Together, these results provide experimental evidence that feeding interactions may enhance the bioavailability of elongated MFs and may facilitate their physical alteration. Our findings underscore the importance of fiber morphology and feeding mode in shaping MF exposure pathways and fate in benthic freshwater ecosystems.