Amazon river prawn is able to express endogenous endo-β-1,4-glucanase and using cellulose as energy source

Abstract

The present study aimed to identify and characterize cellulase from the functional genome in the hepatopancreas of Amazon river prawn (Macrobrachium amazonicum). Growth trials with post-larvae of M. amazonicum validated the endogenous expression of cellulases based on analysis of gene expression via RT-PCR and evaluated the effects of cellulose-rich diet on the growth performance and body composition in the Amazon river prawn. The endo-β-1,4-glucanase gene was identified as a part of the functional genome in the hepatopancreas of M. amazonicum whose entire coding region corresponded to 580 amino acids (aa), with a molecular mass of 63.6 kDa and tertiary structure of the (α/α)6 type. A 60-day growth experiment was designed encompassing five treatments and three replicates using isoprotein (36.98 ± 0.30%) and isoenergetic (19.76 ± 0.18 MJ/Kg) purified diets. The starch in diets was replaced by distinct cellulose levels, ranging from 0% to 35% of cellulose content. The polynomial regression analysis showed that the optimal dietary cellulose level for increased growth performance in post-larvae of M. amazonicum should be between 23.41% and 29.60%. In relation to body composition (crude protein and protein efficiency ratio), the best cellulose values in diets were estimated at 20.54% and 18.97%, respectively. The gene expression analysis via RT-PCR evidenced that endo-β-1,4-glucanase is expressed in prawns fed upon diets containing cellulose from the beginning up to the end of the feeding trial, thus validating the previous genetic assay. Therefore, we conclude that M. amazonicum expresses the endo-β-1,4-glucanase enzyme and prefers diets rich in crude fiber (19–29%), used as a protein-sparing energy source.