Cazyme-Based Strategies to Boost Silage Nutritional Value

GIZZI, F; MARTIN, M; STORANI, A; GUERRERO, SA; IGLESIAS, AA; MAGNI, C; BLANCATO, VS

Rosario

Congreso; LIX Reunión Anual de SAIB; 2023

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

The capacity of ruminants to transform plant biomass into meat and milk is highly dependent on the digestibility of plant cell walls. These cell walls consist of an intricate matrix of carbohydrates, including cellulose, hemicellulose, and pectin. These carbohydrates are linked together by strong bonds that are difficult for ruminal microorganisms to break down. CAZymes include cellulases which hydrolyze cellulose into glucose, and xylanases which hydrolyze xylan into xylose. The use of CAZymes in silage can improve the digestibility of plant cell walls making the carbohydrates more accessible to ruminal microorganisms. This can lead to increased animal productivity and improved feed efficiency. There are several ways in which CAZymes can improve the digestibility of plant biomass for ruminants. First, theycan break down complex carbohydrates into smaller molecules that are more easily digested by ruminal microorganisms. Second, they can release fermentable sugars, which can provide energy for the ruminant animal. Third, they can reduce the viscosity of silage, which can improve the intake and digestion of silage by ruminants. Inoculating silage with concentrated acid lactic bacteria is a common technique that enhances the fermentation of these forages. Lactococcus lactis is a generally regarded as safe (GRAS) lactic acid bacterium recognized as an efficient microbial cell factory. Previously we employed this strain to produce Bacillus subtilis xylanase Bsxyn11A. In this work, we aimed to produce another enzyme, a cellulase, in L. lactis to improve silage quality. To achieve this, the gene was cloned into the expression vector fused with a secretion signal and electroporated to L. lactis. The concentration of inducer and growth time of this strain was optimized to increase protein yield. Then, the activity of the enzyme was evaluated against its specific substrate. Next, biomass degradation capabilities were confirmed by incubation with grounded sorghum and posterior TLC analysis. Finally, culture supernatants of L. lactis producing the enzymes or purified cellulase and/or xylanase enzymeswere combined to enhance biomass degradation and produce a greater release of soluble carbohydrates. The approach followed could provide a cost-effective strategy for optimizing current methods, thereby improving nutritional value of silage. Ultimately, this could lead to increased animal productivity and enhanced feed efficiency.