Modelling digestive hydrolysis of nutrients in fish using factorial designs and desirability function

Abstract

Models simulating the in vitro digestive hydrolysis of nutrients by different animal species are frequently used to obtain a better understanding of factors affecting this process. Optimization algorithm of a model may be used to prospect the more favourable combination of selected factors resulting in the higher performance. This study was conducted to determine the combination of factors (pH, enzyme:substrate ratio, and reaction time) leading to highest bioavailability of proteins and carbohydrates in the gilthead seabream gastrointestinal tract. Besides, a novel multi-objective algorithm, desirability function, was introduced for optimization of the digestive hydrolysis of nutrients within the simulated gut of the species, using models based on the Response Surface Methodology. Design of experiment was defined based on the physiology and culture conditions of the species, and in vitro assays were performed in a two-phase (stomach ad intestine) digestion process, using the species-specific enzyme extract. According to results, intestinal phase of digestion makes the major contribution to the total protein hydrolysis, being the efficiency of the process directly correlated to all the three studied factors. In contrast, the efficiency of carbohydrate hydrolysis was directly correlated to the amount of substrate and inversely to the pH, while reaction time did not exert a significant effect. The physiological range of the factors studied in the assays favoured the hydrolysis of proteins over carbohydrates, a similar scenario to that observed in the live fish. Results from the mathematical models and their simultaneous optimization obtained from this work may have practical applications in design of feeds for this species.

Solid-state fermented brewer's spent grain enzymatic extract increases in vitro and in vivo feed digestibility in European seabass

“…In the present study, the higher pentoses and amino acids release observed in the alkaline stage may have been triggered by the previous stomach digestion, which facilitated protein and carbohydrate hydrolysis during intestinal digestion by increasing substrate accessibility to the enzymes. Similarly, other authors also observed that the acid pre-digestion of fishmeal and plant feedstuffs increased intestinal protein hydrolysis 27 , 59 , reflecting the significant contribution of alkaline digestion in the total protein hydrolysis 60 .…”

Improving and standardizing protocols for alkaline protease quantification in fish

“…The alkaline digestion plays a predominant role in the complete protein breakdown in gastric fish and non‐gastric fish (Gilannejad et al 2018). Knowledge of the activity of alkaline proteases, present in the digestive tract of fish, is very important since non‐gastric fish or fish that do not yet have a developed and functional stomach, they are solely responsible for the digestion of dietary proteins.…”

In-vitro digestion models: a critical review for human and fish and a protocol for in-vitro digestion in fish

“…Comparison between two fish developmental stage [ 166 ] 3.5 & 8 6.25 37 15 & 45 Soybean concentrate on 7 different level DH, Nutrient retention (N, P), Invivo Totaba magnodali [ 83 ] 8 nd 25 60 min Nannochloropsis granulata DH Oncorhynchus mykiss Litopenaeus vannamei Evaluate different treatment by supercritical CO 2 extraction [ 167 ] 3.5–6.5 & 6.5–8.5 125–500 & 50–200 nd. 240–480 & 480–640 Comerical feed FAA Reducing sugar Sparus aurata Two stage membrane reactor, with fish crude extract [ 23 ] 3.5 & nd. nd.…”

“…The in-vitro digestion studies for human has been applied throughout several different applications ( Figure 1 ). Moreover, they were well documented with several globally practiced protocols, while the protocols for fish was limited and highly varied between different authors [ 23 ]. Both fish and humans are monogastric vertebrates, sharing a similar gastrointestinal tract with differences in the anatomical, physiological, and enzymatic features.…”