Since the early 1980s, a large number of studies on enzymes from the red king crab hepatopancreas were conducted. They have been relevant both from a fundamental point of view in terms of studying the enzymes of marine organisms and in terms of rational natural resource management aimed to obtain new valuable products from the processing of crab fishing waste. Most of these works were performed by Russian scientists due to the area and amount of waste of red king crab processing in Russia (or the Soviet Union). However, the close phylogenetic kinship and the similar ecological niches of commercial crab species and the production scale of the catch provide the bases for the successful transfer of experience in the processing of the red king crab hepatopancreas to other commercial crab species caught worldwide. This review describes the value of recycled commercial crab species, discusses processing problems, and suggests possible solutions for these issues. The main emphasis is made on hepatopancreatic enzymes as the most salubrious products of red king crab waste processing.

Anti-fatigue effects of protein hydrolysates are often attributed to low-molecular-weight peptides which are thought to rapidly increase plasma amino acids level. Typically, these peptides are produced using time consuming and labor-intensive procedures to isolate them. Here, we found that a soy protein isolate hydrolysate (SPIH), composed of a complex mixture of peptides with an average molecular weight of ~ 6 kDa, significantly increased endurance in a rat weight-loaded swimming test, prolonging the swimming time by 511%. This shows that a potent anti-fatigue effect can be achieved without isolating low-molecular-weight fractions. Nuclear Magnetic Resonance (NMR) analysis of the concentrations of more than 50 blood metabolites revealed that the anti-fatigue mechanism of SPIH is not correlated with, nor dependent on, an increase in proteinogenic amino acids. This contrasts with whey protein, for which an amino acid-mediated mechanism remains plausible. Furthermore, a principal component analysis (PCA) of the metabolomic data showed that the SPIH group clustered together with the free amino acid-administered group, which showed the poorest endurance. Based on this study, we propose a hypothesis for the anti-fatigue action of this soy protein hydrolysate, suggesting a mechanism distinct from simply increasing circulatory amino acids.

Peptides of hydrolysates of food proteins are an easily digestible source of amino acids necessary for the body to adapt to physical stress. Commercially significant hydrolysates include whey protein, casein, and other animal proteins. Hydrolysates of plant proteins are gaining popularity, but they are less common, then animal ones. Soy protein isolate is promising for obtaining the hydrolysates due to its affordable price and balanced amino acid profile. However, there are no direct studies showing an improvement in the result of physical activity when eating soy protein isolate hydrolysate (SPIH). In this work, for the first time, the study was conducted on the safety and efficacy of SPIH during physical load on model animals (rats). It was shown that the hydrolysate did not lead to pathological changes in the viscera, food intake, and weight of animals did not differ from the control group (animals consumed whey protein). Under physical load rats enteral fed SPIH showed a tendency to adapt more quickly to physical stress than the control group and the group of animals that was fed by free amino acids. The metabolites of animal blood serum were studied by NMR spectroscopy. It was shown that by the 95th minute after feeding in the group of rats receiving SPIH, the difference of proteinogenic amino acids concentrations in blood between individuals was significantly less than in the groups receiving whey protein or a mixture of amino acids. In other words, individual biochemical and physiological characteristics of individuals did not affect the assimilation of amino acids of hydrolysate.