Comparison of Insect Gut Cellulase and Xylanase Activity Across Different Insect Species with Distinct Food Sources
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abstract
Insect guts represent unique natural biocatalyst systems for biocatalyst discovery and biomass deconstruction mechanism studies. In order to guide the further research for enzyme discovery and biodiversity analysis, we carried out comprehensive xylanase and cellulase activity assays for the gut contents of three insect species representing different orders and food sources. The three insect species are grasshopper (Acrididae sp.), woodborer (Cerambycidae spp.), and silkworm (Bombyx mori) to represent the wood-consuming, grass-consuming, and leaf-consuming insects from Orthoptera, Coleoptera, and Lepidoptera orders, respectively. Generally speaking, the enzyme activity assays have shown that the cellulase and xylanase activities for grasshopper and woodborer guts are significantly higher than those of silkworm under various conditions. In addition, both pH and temperature have a significant impact on the enzyme activities in the gut contents. For the grasshopper gut, the means of xylanase and cellulase activities at pH 7 were 3,397 and 404 M mg -1 min -1, which are significantly higher than the activities at pH 4 and 10 (P < 0.05). However, woodborer guts have shown the highest cellulase activity at pH 10. The results suggested that systems similar to woodborer guts could be good resources for discovering alkaline-tolerant enzymes. Moreover, the enzyme activities in response to different substrate concentrations were also analyzed, which indicated that grasshopper gut had particularly high cellulase activity. The enzyme activities in response to the reaction time were also examined, and we found that the enzyme activities (micromolar per milligram per minute) of different insect gut juices in response to the increase of incubation time fit well to the power function equation (E c = K {dot operator} t b) with high coefficients (r 2 > 0.99). The newly developed model serves well to compare the characteristics of the enzyme mixtures among different insect species, which can be applied to other studies of natural biocatalyst systems for the future. Overall, the data indicated that grasshopper and woodborer guts are valuable resources for discovering the novel biocatalysts for various biorefinery applications. 2010 Springer Science+Business Media, LLC.
