Proteoliza sardina i inćuna u slanim otopinama pomoću komercijalnih enzima

Fish sauce production is a very long process and there is a great interest in shortening it. Among the different strategies to speed up this process, the addition of external proteases could be a solution. This study focuses on the eff ect of two commercial enzymes (Protamex and Protex 51FP) on the proteolysis of two fish species traditionally converted into fish sauce: sardine and anchovy, by comparison with classical autolysis. Hydrolysis reactions were conducted with fresh fish at a temperature of 30 °C and under different saline conditions (from 0 to 30 % NaCl). Hydrolysis degree and liquefaction of the raw material were used to follow the process. As expected, the proteolysis decreased with increasing amount of salt. Regarding the fi sh species, higher rate of liquefaction and higher hydrolysis degree were obtained with anchovy. Between the two proteases, Protex 51FP gave better results with both fi sh types. This study demonstrates that the addition of commercial proteases could be helpful for the liquefaction of fi sh and cleavage of peptide bonds that occur during fi sh sauce production and thus speed up the production process.Postoji veliki interes za skraćivanjem procesa proizvodnje ribljeg umaka. Jedno je od mogućih rješenja ubrzavanja tog postupka dodatak proteaza. U ovom je radu ispitan učinak dvaju komercijalnih enzima (Protamex i Protex 51FP) na proteolizu dvije vrste riba koje se tradicionalno koriste za proizvodnju ribljeg umaka, i to sardina i inćuna, te su rezultati uspoređeni s onima dobivenim autolizom proteina. Hidroliza svježih riba provedena je na temperaturi od 30 °C i pri različitim udjelima soli (od 0 do 30 %). Tijekom postupka praćeni su stupanj hidrolize i likvefakcija sirovine. Prema očekivanjima, pri većim je udjelima soli stupanj hidrolize bio manji. Veća likvefakcija uzorka te veći stupanj hidrolize dobiveni su proteolizom inćuna. Primjenom enzima Protex 51FP postignuti su bolji rezultati s obje vrste riba. Rezultati rada pokazuju da dodatak komercijalnih proteaza može povoljno djelovati na likvefakciju ribe i kidanje peptidnih veza tijekom proizvodnje ribljeg umaka, te na taj način ubrzati proces proizvodnje

Copper, zinc and lead isotope signatures of sediments from a mediterranean coastal bay impacted by naval activities and urban sources

Toulon bay is severely impacted by metal contamination induced by past and recent naval activities. In this work, Cu, Zn and Pb isotope compositions and elemental concentrations of fifty-five surface sediments were determined in order to map the spatial distribution of anthropogenic and natural sources along this land-sea continuum. Two sub-systems of Toulon Bay, the Small and Large bays, showed well-marked patterns on metal contamination levels and isotope signatures for Cu and Pb. The Small bay had the highest metal concentrations, and displayed average Pb and Cu isotope compositions of 1.1664 ± 0.0043 (1s, expressed as 206Pb/207Pb ratios) and −0.17 ± 0.19‰ (1s, expressed as δ65CuNIST values), respectively. It contrasted with the Large bay, with moderate to pristine metal concentrations and average Pb and Cu isotope compositions of 1.1763 ± 0.0079 (1s) and +0.08 ± 0.23‰ (1s), respectively. Lead isotope systematics indicated a binary source mixing process involving industrial and natural sources, while Cu isotope systematics showed a ternary mixing process involving two distinct anthropogenic signatures, interpreted as associated to new diffuse anthropogenic sources and old warfare material. In contrast, Zn isotope compositions in the Small and Large bays were practically the same: +0.06 ± 0.05‰ and +0.06 ± 0.11‰ (1s, expressed δ66ZnJMC values), respectively, denoting an overlap between isotope signatures of natural and anthropogenic sources. This study presents the first detailed spatial distributions of Cu and Zn isotope compositions for an aquatic system, and demonstrates the feasibility to use Cu isotopes as tracers of anthropogenic sources in coastal environments

Can cu isotope composition in oysters improve marine biomonitoring and seafood traceability?

This study provides the first geographic and temporal large-scale analysis of Cu stable isotope compositions in indigenous oysters to biomonitor anthropogenic Cu inputs in aquatic systems. It includes oyster samples from French marine environments with distinct Cu-pollution levels and histories and extends over several decades of biomonitoring. Sample series composed of oysters from the same season and similar size/age intended to avoid biological biases. Oysters in macrotidal estuaries (Loire and Gironde, Western France) display fluctuating Cu concentrations without clear temporal trends, challenging to infer anthropogenic influence. Conversely, the time series of their Cu isotope ratios indicate a constant proportion of natural and anthropogenic Cu sources since the 1980s. In contrast, Cu isotope compositions in oysters from the progressively developing locales (urbanization and recreational boating) of Arcachon and Vilaine bays shift positively over time, along with increasing Cu concentrations. This finding suggests a gradual augmentation in the bioaccumulation of anthropogenic Cu over time. Thus, the time series of Cu isotope compositions in oysters is an unambiguous and robust approach to pinpoint anthropogenic Cu contamination. Furthermore, Cu concentrations combined with isotope compositions yield site-specific fingerprints allowing geographic discrimination among oysters. This two-dimensional Cu signature is promising as a tool for seafood traceability

Protex 51FP as a starter for accelerating fish sauce fermentation from anchovy (Stolephorus commersonii)

In this 180-day study, commercial Protex 51FP enzyme effects as a starter culture on anchovy fish sauce fermentation were investigated. Three fish source fermentation groups, including a control group (the anchovy with 25% of salt addition), E group (the anchovy with 25% of salt and 1% of Protex 51FP addition), and E (-s) group (the anchovy with 1% of Protex 51FP and after 6 hours with 25% of salt), were compared. The fish sauce fermentation groups were sampled, packed into glass jars (10 liters), and covered by a lid at ambient temperature (22 - 30°C) for 180 days. Three commercial fish sauces were also included as nutritional references. The results showed that the addition of Protex 51FP achieved positive results of total nitrogen content and amino acids compared to the control samples (p<0.05). These values were competitive with commercial product figures. Total amino acids in 8000mg/100ml fish sauce were significantly higher than those in the control. There were rich in essential amino acids (41-43%) and small peptides (13% peptides with a molecular weight below 200 Da, 32-39% peptides with a molecular weight below 130 - 200 Da, and 25-28% of peptides with a molecular weight below 200 – 360 Da). Compared with traditional methods, the addition of Protex 51FP (p<0.05) could improve the quality of fish sauce and obtain greater nutritional values. In all experiments, the color of adding-enzyme samples was darker than that of the traditional products, and the smell of these samples (including traditional methods) was not as quite strong as commercial products

Ultrasound-assisted extraction of R-phycoerythrin from Grateloupia turuturu with and without enzyme addition

The aim of this study was to compare two processes for the extraction of R-phycoerythrin (R-PE) from the red seaweed Grateloupia turuturu: ultrasound-assisted extraction (UAE) and ultrasound-assisted enzymatic hydrolysis (UAEH). Process efficiencies were both evaluated by the yield of R-PE extraction and by the level of liquefaction. Experiments were conducted at 40 and 22 °C, for 6 h, using an enzymatic cocktail and an original ultrasonic flow-through reactor. R-PE appeared very sensitive to temperature, thus 22 °C is strongly recommended for its extraction by UAEH or UAE. However, the higher processing temperature (40 °C) clearly increased the extraction of water-soluble compounds (up to 91% of liquefaction). These two new processes are thus promising alternatives for the extraction of water-soluble components including R-PE, from wet seaweeds, with extraction yields at least similar to conventional solid–liquid extraction

Trace metal concentrations in the muscle of seven marine species: Comparison between the Gulf of Lions (North-West Mediterranean Sea) and the Bay of Biscay (North-East Atlantic Ocean)

Concentrations of 6 trace metals (Ag, Cd, Cu, Ni, Pb, Zn) in the muscle of 2 sharks (Galeus melastomus and Scyliorhinus canicula), 4 teleosts (Helicolenus dactylopterus, Lepidorhombus boscii, Micromesistius poutassou and Phycis blennoides) and 1 crustacean (Nephrops norvegicus) were compared between the Bay of Biscay (Atlantic Ocean) and the Gulf of Lions (Mediterranean Sea). Although average concentrations and the trace element pollution index were generally higher in the Gulf of Lions, significant differences between the two ecosystems were only found for Zn for Helicolenus dactylopterus, and for Ag and Cu for the crustacean N. norvegicus. Moreover, some relationships between trophic level or size and metal concentrations were found for these two species. The absence of clear pattern may result from the blurring effect of contamination and excretion that may act differentially for all species and all elements

Differences in Copper Isotope Fractionation Between Mussels (Regulators) and Oysters (Hyperaccumulators): Insights from a Ten-Year Biomonitoring Study

Copper (Cu) isotope compositions in bivalve mollusks used in marine-monitoring networks is a promising tool to monitor anthropogenic Cu contamination in coastal and marine ecosystems. To test this new biomonitoring tool, we investigated Cu isotope variations of two bivalves—the oyster Crassostrea gigas and the mussel Mytilus edulis—over 10 years (2009–2018) in a French coastal site contaminated by diffuse Cu anthropogenic sources. Each species displayed temporal concentration profiles consistent with their bioaccumulation mechanisms, that is, the Cu-regulating mussels with almost constant Cu concentrations and the Cu-hyperaccumulating oysters with variable concentrations that track Cu bioavailability trends at the sampling site. The temporal isotope profiles were analogous for both bivalve species, and an overall shift toward positive δ65Cu values with the increase of Cu bioavailabilities was associated with anthropogenic Cu inputs. Interestingly, mussels showed wider amplitudes in the isotope variations than oysters, suggesting that each species incorporates Cu isotopes in their tissues at different rates, depending on their bioaccumulation mechanisms and physiological features. This study is the first to demonstrate the potential of Cu isotopes in bivalves to infer Cu bioavailability changes related to anthropogenic inputs of this metal into the marine environment

Cu and Zn stable isotopes in suspended particulate matter sub-fractions from the Northern Bay of Biscay help identify biogenic and geogenic particle pools

Marine suspended particulate matter (SPM) plays a pivotal role in the marine biogeochemical cycling of trace elements. This study investigates metal distributions and copper (Cu) and zinc (Zn) stable isotope ratios in different size fractions of SPM from two sampling stations on the inner continental shelf of northern Bay of Biscay (NE Atlantic), a zone highly influenced by the macrotidal Loire estuary, the outlet of a major European river. The objective of this study is to test stable isotopes as tools to infer the origins of particles and their formation processes, and to infer relevant Cu and Zn biogenic pools involved in marine trophic transfers of these metals. SPM samples were nearly quantitatively mineralized (i.e., without HF) to determine metals and Cu and Zn isotopes in their more labile and reactive phases. Their δ65CuSRM-976 values ranged from −0.45 to +0.51‰, with higher Cu concentrations accompanying particle size decreasing. The δ66ZnJMC-Lyon values in SPM sub-fractions varied from +0.14 to +0.76‰, and were uncorrelated to both Zn concentrations and particle size. Compared to larger size fractions, increased Al and Fe levels (proxies for terrigenous materials) and enrichments in lighter Cu and Zn isotopes observed in the smaller size SPM sub-fractions suggest that a major proportion of SPM Cu and Zn is associated with geogenic particles. Conversely, the relative enrichment of heavy isotopes in coarser particles is attributable to an increase of Cu and Zn metabolically incorporated into biogenic organic particles (e.g., plankton), and by surface adsorption onto organic detrital particles. The higher δ-values attributed to biogenic particles likely represents the isotope composition of the local marine organic matter available to primary consumers like filter-feeders (oysters). Thus, this study shows that targeting particles of specific size classes allows to identify relative dominances of biogenic and geogenic carrier phases. Identifying these pools and their isotopic composition may help track Cu and Zn transfers through marine food-web metal in future studie

Kinetic study of solid phase demineralization by weak acids in one-step enzymatic bio-refinery of shrimp cuticles

We describe a one-step bio-refinery process for shrimp composites by-products. Its originality lies in a simple rapid (6 h) biotechnological cuticle fragmentation process that recovers all major compounds (chitins, peptides and minerals in particular calcium). The process consists of a controlled exogenous enzymatic proteolysis in a food-grade acidic medium allowing chitin purification (solid phase), and recovery of peptides and minerals (liquid phase). At a pH of between 3.5 and 4, protease activity is effective, and peptides are preserved. Solid phase demineralization kinetics were followed for phosphoric, hydrochloric, acetic, formic and citric acids with pKa ranging from 2.1 to 4.76. Formic acid met the initial aim of (i) 99 % of demineralization yield and (ii) 95 % deproteinization yield at a pH close to 3.5 and a molar ratio of 1.5. The proposed one-step process is proven to be efficient. To formalize the necessary elements for the future optimization of the process, two models to predict shell demineralization kinetics were studied, one based on simplified physical considerations and a second empirical one. The first model did not accurately describe the kinetics for times exceeding 30 minutes, the empirical one performed adequately

Soft liquefaction of the red seaweed Grateloupia turuturu Yamada by ultrasound-assisted enzymatic hydrolysis process

Ultrasound-assisted enzymatic hydrolysis is a recent process, increasingly employed for plant biomass liquefaction and the recovery of soluble biomolecules. However, to our knowledge, it has never been used on seaweeds, particularly wet ones. The aim of this study was to compare the efficiency of three processes on the liquefaction of the red seaweed Grateloupia turuturu Yamada: enzyme-assisted extraction (EAE), ultrasound-assisted extraction (UAE), and their combination, ultrasound-assisted enzymatic hydrolysis (UAEH). These comparisons will allow the identification as to which process achieves the highest extraction yield of water-soluble compounds. For this purpose, experiments were conducted at 40 °C for 6 h using an enzymatic cocktail of four industrial carbohydrases and an original ultrasonic flow-through reactor. After 6 h, similar profiles were observed between EAE and UAE with the recovery of 71–74 % of the initial material into the soluble phase. However, when these processes were combined, up to 91 % solubilized material was observed in the same time, with a synergistic effect after 2 h. From a biochemical point of view, UAEH improved the extraction of nitrogen and carbon compounds and, more precisely, carbohydrates and amino acids. This study demonstrates that ultrasound improved the enzymatic hydrolysis, probably by an increase in the mass transfer and a disruption of the thallus due to the implosion of the cavitation bubbles generated. UAEH is clearly an efficient procedure for the liquefaction of wet seaweeds, enabling the recovery of valuable components