Characterization of Gastric-Intestinal Stability for Processive Endoglucanases as Exogenous Fibre Enzymes in Pigs

Background

Poor utilization of dietary fibre limits pig production profit margin largely due to that current exogenous feed fibre enzymes are originated from Trichoderma and Aspergillus species with limited stability and efficacy. Two processive endoglucanases, referred to as tCel5A1 and pCel4818_2A, are reported to hydrolyze natural cellulose and have multi-functionality towards hemicelluloses (Basit and Akhtar, Biotechnology and Bioengineering 2018, 115:1675; Wang et al., Scientific Reports 2019, 9:13630). This study was to investigate the gastric-intestinal stability in vitro for these two novel endoglucanases.

Methodology

Cel5A and pCel4818_2A were overexpressed in ClearColi®BL21(DE3). Endoglucanase activity was determined with 0.70% sodium carboxymethyl cellulose and 5 mM dithiothreitol, purged with pressured N2 and incubated at pH 6.5 – 7.0 and 37 °C for 15 min.

Results and discussion

After incubating the enzymes in vitro under the porcine gastric pH (3.5), pepsin activity (274 U/mL) as well as intestinal trypsin (78 U/mL) and chymotrypsin (20 U/mL) activities at pH 6.5 during 0 – 5 h, the Eadie-Hofstee analyses shown that tCel5A1 and p4818Cel5_2A cellulases respectively lost about 18 and 68% of their initial activities after 2 h under the gastric conditions; and lost more than 90% of their initial activities after 2 – 3 h under the intestinal conditions.

Conclusions

Enzyme protein engineering or post-fermentation treatment such as coating for by-passing the gastric-intestinal environment would be needed to enable these two cellulases as efficacious exogenous fibre enzymes.

Applicability and benefits of research to industry

Gastric-intestinal stability should be an important consideration for developing new cellulases and for assessing efficacy of current exogenous feed enzymes in swine dietary applications.

Take home message

Gastric-small intestinal stable and efficacious multifunctional cellulases will dramatically improve dietary fibre utilization and pork production profit.

Key words: fibre, cellulase, pig nutrition.

Presented at the 2021 Animal Nutrition Conference of Canada. For information on the next edition, click here.