Lipid characterization and properties of protein hydrolysates obtained from discarded Mediterranean fish species.

BACKGROUND: Discards are an important fraction of the by-products produced by the fishing industry. As a consequence of their low commercial acceptance, it is necessary to provide added value to these underutilized materials. In this study the lipid fraction of three discarded fish species in the western Mediterranean Sea, namely sardine (Sardina pilchardus), mackerel (Scomber colias) and horse mackerel (Trachurus trachurus), was characterized and the angiotensin I-converting enzyme (ACE)-inhibitory and antioxidative activities of their protein hydrolysates were evaluated. RESULTS: Processing of these biomaterials led to oils with a high content of omega-3 polyunsaturated fatty acids (PUFAs), ranging from 220.5 g kg(-1) for horse mackerel to 306.0 g kg(-1) for sardine. Regarding the protein fraction, most of the hydrolysates presented ACE inhibition values higher than 60%, corresponding to IC50 values varying from 345 µg protein mL(-1) for mackerel to 400 µg protein mL(-1) for sardine. Moreover, most of the hydrolysates exhibited acceptable antioxidative activity, namely 35-45% inhibition of 1,1-diphenyl-2-picrylhydrazyl (DPPH). CONCLUSION: This study suggests that the three discarded species evaluated are valuable raw materials for the production of bioactive ingredients such as omega-3 PUFAs and protein hydrolysates exhibiting antihypertensive and antioxidative activities.

Water quality characterization in real biofilm wastewater treatment systems by particle size distribution.

This article analyses the relation between wastewater quality parameters and particle size distribution (PSD) in three real wastewater treatment plants with different biofilm technologies: submerged biofilter system, trickling filter system, and rotating biological contactor system. The main quality parameters, (suspended solids, turbidity and COD), and PSD in the influent and effluent water of each different biofilm treatment were analyzed during 1year. The PSD was fitted using the power law (n(d(p))= partial differentialN(d(p))/ partial differentiald(p)=A x d(p)(-)(b)(Log(d)(p)())) obtaining the coefficients A and b to define the particle distribution. Mathematical correlations between this coefficients and the rest of parameters studied were found (SS=0.0713 x A(0.585), turbidity=4.549 x 10(-4) x A(1.096), COD=0.0201 x A(0.774)). The relation with the average particle size by mass was also found, (d(pma)=60.3137 x b(-2.242)). Moreover a relation between PSD and the particle elimination efficiency of the secondary treatment was study, (eta=2.844-2.498 x b(relative)+0.0863 x A(relative)). These expressions are very useful to understand the behavior of the biofilm treatment system using PSD analyses.