Chitin

About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.

The cell wall stress response in Aspergillus niger involves increased expression of the glutamine : fructose-6-phosphate amidotransferase-encoding gene (gfaA) and increased deposition of chitin in the cell wall

Abstract: Perturbation of cell wall synthesis in Saccharomyces cerevisiae, either by mutations in cell wall synthesis-related genes or by adding compounds that interfere with normal cell wall assembly, triggers a compensatory response to ensure cell wall integrity. This response includes an increase in chitin levels in the cell wall. Here it is shown that Aspergillus niger also responds to cell wall stress by increasing chitin levels. The increased chitin level in the cell wall was accompanied by increased transcription of gfaA, encoding the glutamine: fructose-6-phosphate amidotransferase enzyme, which is responsible for the first and a rate-limiting step in chitin synthesis. Cloning and disruption of the gfaA gene in A. niger showed that it was an essential gene, but that addition of glucosamine to the growth medium could rescue the deletion strain. When the plant-pathogenic fungus Fusarium oxysporum and food spoilage fungus Penicillium chrysogenum were subjected to cell wall stress, the transcript level of their gfa gene increased as well. These observations suggest that cell wall stress in fungi may generally lead to activation of the chitin biosynthetic pathway. © 2004 SGM.

Fungal chitinases: function, regulation, and potential roles in plant/pathogen interactions

Abstract: In the past decades our knowledge about fungal cell wall architecture increased tremendously and led to the identification of many enzymes involved in polysaccharide synthesis and remodeling, which are also of biotechnological interest. Fungal cell walls play an important role in conferring mechanic stability during cell division and polar growth. Additionally, in phytopathogenic fungi the cell wall is the first structure that gets into intimate contact with the host plant. A major constituent of fungal cell walls is chitin, a homopolymer of N-acetylglucosamine units. To ensure plasticity, polymeric chitin needs continuous remodeling which is maintained by chitinolytic enzymes, including lytic polysaccharide monooxygenases N-acetylglucosaminidases, and chitinases. Depending on the species and lifestyle of fungi, there is great variation in the number of encoded chitinases and their function. Chitinases can have housekeeping function in plasticizing the cell wall or can act more specifically during cell separation, nutritional chitin acquisition, or competitive interaction with other fungi. Although chitinase research made huge progress in the last decades, our knowledge about their role in phytopathogenic fungi is still scarce. Recent findings in the dimorphic basidiomycete Ustilago maydis show that chitinases play different physiological functions throughout the life cycle and raise questions about their role during plant-fungus interactions. In this work we summarize these functions, mechanisms of chitinase regulation and their putative role during pathogen/host interactions.

Improved Colorimetric Determination of Cell Wall Chitin in Wood Decay Fungi

Abstract: The Svennerholm modification of the Elson-Morgan method for glucosamine analysis was evaluated for its applicability to the rapid determination of chitin in wood decay fungi. The evaluation included extent of chromogen interference, sensitivity, color stability, and hydrolysis conditions for maximum release of glucosamine from fungal cell walls. With our further modification, the Svennerholm method was shown to be suitable for rapid quantitative determination of fungal chitin without chromatographic separation of hydrolysate chromogens.

Chitin and chitosan-based support materials for enzyme immobilization and biotechnological applications

Abstract: Enzymes of industrial importance are primarily employed for biotechnological applications. However, high-cost and instability issues of purified enzymes hamper their usage. Multiple reuses rather than the single use is more cost-effective. A robuster bioprocess is feasible by enzyme immobilization. Performance of immobilized enzymes depends on the nature of support materials. Chitin and its derivatives-based supports offer stability and cost-effective bioprocessing. Chitosan is biocompatible, biodegradable, non-toxic and has multiple functional groups. A variety of supports such as chitosan, chitosan film, chitosan nanoparticle and chitosan nanocomposite are employed for enzyme immobilization. Chitosan bound enzymes, as compared to free enzymes, have improved the biocatalytic performances due to exceptionally high operational stability and reusability. Here we review enzymes immobilized on chitin/chitosan supporting materials with applications ranging from agriculture to drug delivery.