Chitosan Mitigates Bacterial Infection-induced Metabolic Stress in Silkworms: A Study on Carbohydrate and Amylase Dynamics

Abstract

Silkworm (Bombyx mori L.) rearing is a cornerstone of India's rural economy but is frequently hampered by infections such as flacherie, caused by Staphylococcus aureus and Bacillus thuringiensis. This study evaluated the influence of silkworm pupal chitosan extracted via deproteinization, demineralization, deacetylation and decolorization from commercial pupae and exuviae, on haemolymph carbohydrate content and amylase activity during infection. Fifth-instar larvae were orally inoculated with 10⁸ CFU/mL of either bacterial strain, followed by feed treatments of chitosan at 3500–5000 ppm, commercial chitosan at 1000 ppm and ampicillin at 1000 ppm, administered at intervals of 6, 12, 18, 24 and 30 hours after bacterial inoculation. Haemolymph sampling from days 2 through 8 revealed that early chitosan applications (within 6-18 hours) significantly enhanced carbohydrate reserves and amylase enzyme activity compared to controls, with higher responses seen during S. aureus infection. Delayed treatment showed attenuated effects. These results suggest that pupal chitosan augments nutrient utilization and enzymatic mobilization, mitigating the metabolic stress induced by bacterial pathogens. Timely administration of silkworm-derived chitosan therefore represents a promising, sustainable and cost-effective bioagent for improving disease resilience and productivity in sericulture.