Species-specific thermal denaturation pattern of fish myosin when heated as myofibrils as studied by myosin subfragment-1 and rod denaturation rates

Thermal denaturation of myofibrils from various species of fish was investigated by measuring ATPase inactivation, myosin aggregation, myosin subfragment-1 (S-1) and rod denaturation rates as studied by chymotryptic digestion. Decrease in monomeric myosin (myosin aggregation) was always faster than the ATPase inactivation for all myofibrils tested. The relative denaturation rate of rod to that of S-1 differed from species to species. Preceded denaturation of rod was observed with some species, and the opposite was true with other species. The denaturation pattern was explained by the different magnitude of S-1 stabilization by F-actin in myofibrils at low salt medium. Myofibrils which receive a great stabilization by F-actin as studied by ATPase inactivation showed the preceded rod denaturation pattern, and vice versa. S-1 portion, not F-actin, determined the different stabilization of S-1 by F-actin in myofibrils.     

Effect of calcium ion on the thermal denaturation of subfragment-1 and rod regions of squid myosin upon the heating of myofibrils

Thermal inactivation of Ca²⁺ ATPase of squid myofibrils was significantly suppressed in the presence of Ca²⁺. Monomeric myosin content decreased much faster than Ca²⁺ ATPase inactivation in Ca medium, which was well explained by fast rod denaturation. In contrast, rod denaturation was slower than S-1 in EDTA medium. The decrease in monomeric myosin content was explained by faster S-1 denaturation. Comparing the S-1 and rod denaturation rates at a fixed temperature, it was concluded that S-1 denaturation was suppressed by Ca²⁺ whereas the rod denaturation was not. An unfolding experiment with isolated myosin rod confirmed that there was no stabilizing effect of Ca²⁺ on myosin rod. It was concluded that significant stabilization of the S-1 portion by Ca²⁺ generated the apparently different myosin denaturation patterns in the two media.     

Denaturation mode of carp myofibrils when affected by temperature and salt concentration

ABSTRACT: Heating temperatures of 30–40°C and KCl concentrations of 0.1–0.5 M altered the denaturation mode of carp myofibrils. In 0.1 M KCl medium, heating temperature affected the denaturation of rod more significantly than of subfragment-1 (S-1), and a slow decrease in solubility at 30°C was accompanied by a slow denaturation of rod. KCl concentration at heating altered the denaturation mode differently at 30°C and 40°C. Increased KCl concentrations for heating reduced the rod denaturation rate at 40°C, but it was increased at 30°C. At concentrations above 0.3*Τ*M KCl, the denaturation rate for rod became identical to that for S-1 at both temperatures. Upon heating of chymotryptic digest of myofibrils, S-1 denaturation was similarly detected as in intact myofibrils, whereas practically no rod denaturation was detected. Thus, it was concluded that myosin structure connecting S-1 and rod has an important role in the denaturation process.     

Comparative study on thermal denaturation modes of myosin in walleye pollack and carp myofibrils as affected by salt concentration

ABSTRACT:   The effect of salt concentration on the thermal denaturation profile of myosin in walleye pollack and carp myofibrils was compared by studying the subfragment-1 (S-1) and rod denaturation rates upon heating. Species-specific denaturation mode observed at 0.1 M KCl was no longer detected when samples were heated above 0.5 M KCl, where S-1 and rod denaturation rates were identical to each other. As the heating of the chymotryptic digest of myofibril formed practically no rod aggregates, S-1 denaturation in a form of myosin was the rate limiting step for rod aggregate formation. As the aggregate formation by rod was remarkably suppressed by lowering the temperature, the free movement of myosin tail upon heating was suggested to play an important role in the rod aggregate formation in a high salt medium.     

Myosin denaturation in heated myofibrils of scallop adductor muscle

The thermal inactivation of Ca²⁺ ATPase of scallop myofibrils (0.1 M KCl, pH 7.5) was found to be unaffected by the presence of Ca²⁺. Monomeric myosin content and salt solubility decreased much faster than Ca²⁺ ATPase inactivation in both Ca and EDTA media, which was well explained by faster denaturation of the rod portion than subfragment-1 of myosin. In contrast, when the myofibrils were heated at 0.5 M KCl, a slow decrease in salt solubility was observed, which was also explained by slow denaturation of the rod portion of myosin. Myofibrils from scallop smooth muscle showed the same denaturation pattern as those from adductor muscle. These results show that mollusk myosin is not always stabilized by Ca²⁺.     

Myosin denaturation in “Burnt” Bluefin tuna meat

A quantitative conversion of tuna meat into muscle homogenate made it possible to study myosin denaturation in Bluefin tuna meat. Myosin denaturation was accessed by measuring Ca²⁺-ATPase activity, salt-solubility with and without Mg-ATP, monomeric myosin content, and amount of subfragment-1 (S-1) and rod produced by chymotryptic digestion. Commercially available tuna used in this study showed a pH around 5.4–5.7. Myosin in the meat lost the salt-solubility measured in the absence of Mg-ATP; however, such myosin showed full salt-solubility when released from actin in the presence of Mg-ATP. Incubation of tuna meat at 30 °C for up to 90 min caused obvious myosin denaturation. However, the tuna meat dialyzed against neutral pH buffer showed practically no myosin denaturation by the same heating. It was suggested that exposure to lowered pH to around 5.5 and increased temperature of 30 °C led myosin denaturation. Myosin denaturation in the “Burnt” Bluefin tuna sample was analyzed. A significant myosin denaturation was observed with the part showing the “Burning” symptom, the inner part of the tuna meat near the spine. Myosin in that part showed almost no Ca²⁺-ATPase activity, no salt-solubility even with Mg-ATP, no recovery of monomeric myosin, and almost no production of S-1 by chymotryptic digestion. However, myosin denaturation was not detectable for the meat taken from outer parts of the same tuna near the skin with normal appearance. It was demonstrated that “Burning” of tuna meat occurring in the deep part of the body is accompanied by myosin denaturation. The above results suggested that insufficient cooling of the deep part of body would be the reason for “Burning” of tuna meat.     

Different effects of ionic and non-ionic compounds on the freeze denaturation of myofibrils and myosin subfragment-1

The effects of non-ionic (sorbitol, maltose, trehalose) and ionic compounds (Na-glutamate, Na-acetate, Na-sulfate, ammonium sulfate) on freeze denaturation of myosin subfragment-1 (S-1) and of myofibrils were compared. Sugars, Na-glutamate and Na-acetate well suppressed the freeze denaturation of myofibrils as well as S-1 in a concentration dependent manner. Although sulfate suppressed freeze denaturation of S-1 irregularly, it accelerated myofibril denaturation. It was concluded that sulfate salts were useless as cryoprotectant for myofibrils. Stabilization extent by F-actin in frozen storage was much less than that in heating.     

Suppressing effect of neocarrabiose 4-O-sulfate on thermal and freeze denaturation of myosin subfragment-1 and myofibrils

Suppressive effects of neocarrabiose 4-O-sulfate on the thermal and freeze denaturation of myosin subfragment-1 (S-1) and on myofibrils were investigated. The compound strongly suppressed the thermal denaturation of S-1. Its suppressive effect was greater than that of sorbitol and similar to that of maltose. However, it tended to accelerate the denaturation of myofibrils, suggesting a loss of protection by F-actin upon its addition. The compound suppressed the freeze denaturation of myofibrils and S-1. The effect was similar to that of sorbitol or maltose, and completely different from that of Na-sulfate. The compound solubilized myofibrils at concentrations similar to KCl. Therefore, it was concluded that neocarrabiose 4-O-sulfate behaved as an ionic salt in the thermal treatment process, whereas it behaved as a sugar in the frozen storage process.     

Stabilization of myosin by ionic compounds as affected by F-actin

ABSTRACT:   Suppressive effects of non-ionic (sorbitol, maltose, and trehalose) and ionic (Na-glutamate, Na-acetate, Na-sulfate, and ammonium sulfate) compounds on the thermal inactivation of myosin subframgent-1 (S-1) and myofibril Ca²⁺-ATPase were compared. All compounds suppressed S-1 denaturation. When myofibrils were used (at 0.1 M KCl), sugars and sugar alcohol (non-ionic compounds) suppressed denaturation similar to S-1, while Na-glutamate, Na-acetate, and Na-sulfate weakly suppressed them. Ammonium sulfate accelerated denaturation, but suppressed denaturation when heated in 2 M KCl, at which myosin lost protection by F-actin. It was thus concluded that ionic compounds affected the denaturation of myofibrils in two ways; suppression as established with S-1, and acceleration as a result of loss of protection by F-actin caused by increase in ionic strength.     

Myosin and actin denaturation in frozen stored kuruma prawn Marsupenaeus japonicus myofibrils

Myosin and actin denaturation in kuruma prawn myofibrils stored frozen (0.1 M NaCl, pH 7.5) at ?20 °C was investigated. The inactivation profile of Ca²⁺-ATPase in the myofibrils was identical to that for myosin, indicating that myosin in myofibrils was not protected by actin. The presence of myosin detached from actin in the soluble fraction was proven by ammonium sulfate fractionation in the absence and presence of Mg-ATP. Actin denaturation in myofibrils was further confirmed by its increased susceptibility to chymotryptic degradation. In the frozen myofibrils, actin denatured more rapidly quicker than myosin: actin had completely denatured by storage day 1, followed by a gradual denaturation of myosin. Both myosin and actin in the frozen stored myofibrils retained their high salt-solubility, which decreased slowly during the frozen storage period. The presence of aggregated inactivated myosin in the salt-soluble fraction was proven by precipitation at 40 % saturation of ammonium sulfate in the presence of Mg-ATP, leaving active monomeric myosin in the soluble fraction. Almost no actin denaturation was observed with heated myofibrils.     

Stabilizing effect of Ca<Superscript>2+</Superscript> on myosin and myofibrils of squid mantle muscle as affected by heating conditions

The suppressive effects of Ca²⁺ on the thermal denaturation of myosin and myofibrils of squid mantle muscle were compared. The stabilization effect on myosin was smaller than that on myofibrils and was not affected by KCl concentration. The stabilizing effect of Ca²⁺ on myosin decreased as the heating temperature dropped, showing no stabilization at 20°C, while the effect on myofibrils was the same at all temperatures tested. The stabilizing effect of Ca²⁺ on myosin disappeared even at 30°C in the presence of sorbitol, where a small inactivation rate was found, while the effect of Ca²⁺ on myofibrils was equally detected irrespective of the reduction in inactivation rate in the presence of sorbitol. Stabilization of myosin by Ca²⁺ again appeared even in the presence of sorbitol when the heating temperature was raised to 38°C. It was suggested that Ca²⁺ confers stabilization on myosin only when myosin is under unstable conditions. The stabilization effect of Ca²⁺ on myosin was enhanced upon F-actin binding: Ca²⁺-bound myosin was more significantly stabilized by F-actin binding, and the effect was no longer affected by the conditions for heating.     

Pond farming of Nile tilapia, Oreochromis niloticus (L.)j in northern Cameroon. Controlling a sexing error of 1% in hand-sexed male tilapia monosex culture by African catfish, Clarias gariepinus (Burchell)

Catfish (mean W₀ 189 g) were added to ponds (525 m^J each) stocked with 230 hand-sexed, male tilapia (W_u163 g), at 0.04, 0.10 and 0.15 catfish m^?2. In each pond, two female tilapias were introduced, thereby creating a sexing error of less than 1%. Feeding was fixed throughout the experiment at 2.5 kg of cottonseed cake per day per pond 6 days per week (mean feeding rate R = 41 kg ha^?1 day-¹). Rearing time was 125 days. Average net pond production per treatment (ranging between 7.5 and 7.9 t ha^?1 year^?1) and marketable production were not different between treatments but net tilapia production was significantly lower at the highest catfish density. Both catfish and tilapia growth were negatively correlated with catfish density due to feed competition near the end of the experiment. It was concluded that catfish efficiency in controlling tilapia recruitment was strongly reduced by the availability of supplementary high-protein feed. Large catfish competed with the parent tilapia for the cottonseed cake but apparently did not exploit the tilapia recruits. Yield of tilapia recruits was lowest at the highest catfish fingerling density, although this was not significant. The number of catfish fingerlings was significantly higher at the lowest catfish density, which indicated that large catfish preyed on catfish fingerlings.     

Pond farming of Nile tilapia, Oreochromis niloticus (L.), in northern Cameroon. Adding hand-sexed male tilapia to graze the dense algal blooms in ponds with African catfish, Clarias gariepinus (Burchell)

Four earthen ponds (250 m² each) were stocked each with 250 small catfish (W₀=39g). In treatment A, African catfish. Clarias gariepinus (Burchell), were raised in monoculture, while in treatment B catfish were raised in polyculture with an additional 125 male Nile tilapia, Oreochromis niloticus (L.) (W₀=44g). Feeding of cottonseed cake was at about 4% of catfish body weight day^?1. Daily feed quantities, however, were averaged over all four ponds so that each pond received the same amount of cottonseed cake. Rearing time was 118 days. In treatment A, catfish grew to an average weight of 200g. In treatment B, catfish reached 158g and tilapia 185g, Extrapolated marketable fish production was strikingly similar in all four ponds (around 4.8 t ha^?1 year^?1). No synergistic effect was obtained by stocking microphagous tilapia, although the feeding of cottonseed cake enhanced dense algal blooms in all ponds. Catfish did not appear to exploit the tilapia recruits, as an indirect pathway of algae cropping.     

Cage‐pond integration of African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) with carps

Cage‐pond integration system is a new model for enhancing productivity of pond aquaculture system. A field trial was conducted using African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) in cages and carps in earthen ponds. There were four treatments replicated five times: (1) carps in ponds without cage, (2) tilapia at 30 fish m^?3 in cage and carps in open pond, (3) catfish at 100 fish m^?3 in cage and carps in open pond, (4) tilapia and catfish at 30 and 100 fish m^?3, respectively, in separate cages and carps in open pond. The carps were stocked at 1 fish m^?2. The cage occupied about 3% of the pond area. The caged tilapia and catfish were fed and the control ponds were fertilized. Results showed that the combined extrapolated net yield was significantly higher (P < 0.05) in the catfish, tilapia and carps integration system (9.4 ± 1.6 t ha^?1 year^?1) than in the carp polyculture (3.3 ± 0.7 t ha^?1 year^?1). The net return from the tilapia and carps (6860 US$ ha^?1 year^?1) and catfish, tilapia and carps integration systems (6668 US$ ha^?1 year^?1) was significantly higher than in the carp polyculture (1709 US$ ha^?1 year^?1) (P < 0.05). This experiment demonstrated that the cage‐pond integration of African catfish and Nile tilapia with carps is the best technology to increase production; whereas integration of tilapia and carp for profitability.     

Effect of Cryoprotectants on Suppression of Protein Structure Deterioration Induced by Freeze-thaw Cycle in Pacific White Shrimp

This study aimed to elucidate the changes in Pacific white shrimp (Litopenaeus vannamei) myofibrillar protein as influenced by multiple freeze-thaw cycles as well as the stabilization effects of sucrose and trisodium citrate on shrimp myofibrils. Shrimp myofibrils in 0.1 M NaCl, 20 mM Tris-HCl (pH 7.5) were mixed individually with sucrose and citrate at concentrations of 0.05 M and were evaluated for Ca²⁺-ATPase activity, salt solubility, total and reactive sulfhydryl, and surface hydrophobicity during three freeze-thaw cycles. Sucrose and citrate had strong cryoprotective effects against freeze denaturation by retaining higher Ca²⁺-ATPase activity and salt-soluble myosin and actin, by slowing the reduction of reactive sulfhydryl (SH) and by exposing less hydrophobic groups at the surface of the protein compared with the no-additive sample. Results indicated that both cryoprotectants had suppressive effect against protein denaturation and helped stabilize white shrimp myofibrillar protein during the freeze-thaw process. This study suggests that sucrose and citrate stabilized the protein structure by retarding the unfolding of protein; thus, the native protein could be protected during frozen storage.     

Pond farming of Nile tilapia, Oreochromis niloticus (L.), in northern Cameroon. Feeding combinations of cottonseed cake and brewery waste in fingerling culture, hand-sexed male monosex culture, and mixed culture with police-fish, Clarias gariepinus (Burchell)

Twelve production trials were analysed retrospectively, covering three different rearing methods in which Nile tilapia, Oreochromis niloticus (L.), were fed with combinations or cottonseed cake and brewery waste. Highest extrapolated net pond productions, including tilapia recruits, were obtained in tilapia fingerling rearing (W₀ <10 g; 11.8 t ha^?1 year^?1). Stocking African catfish, as police-fish (0.2 catfish m^?2) in mixed tilapia (W₀ > 90 g) culture was effective in controlling tilapia recruitment, but net pond production was low (4.1 t ha^?1 year^?1). Hand-sexing of male tilapias (W₀ > 90 g) only limited recruitment but resulted in a significantly higher net pond production (8.6 t ha^?1 year^?1) than in mixed culture. Extrapolated marketable production in the treatment stocked with hand-sexed tilapia males (tilapia only) was also higher than the extrapolated marketable production in the mixed culture treatment (tilapia and catfish combined), although this difference was not significant. Extrapolated net pond production and extrapolated net tilapia production were both significantly correlated to the daily feeding rate of cottonseed cake but not to the daily feeding rate of brewery waste. The high relative FCRs of the feed mixture were probably due to the brewery waste.     

Improved solubility and stability of carp myosin by conjugation with alginate oligosaccharide

ABSTRACT:   Carp myosin was conjugated with alginate oligosaccharide (AO) through the Maillard reaction under low relative humidity, and the functional properties of the myosin-AO conjugate were investigated to clarify the role of myosin in the functional improvement of fish myofibrillar proteins (Mf) by the glycosylation. The findings were as follows. First, myosin became highly solubilized at lower NaCl concentrations by conjugation with AO and NaCl-dependence of the solubility was lost when > 12% of the available lysine residues were reacted with AO and 50 µg/mg of AO was attached to myosin. Second, the thermal stability of myosin was effectively improved by conjugation with AO. Heat-treatment at 50°C for 6 h has no effect on the solubility of the myosin-AO conjugate regardless of the NaCl concentration. Third, the improved functionalities of myosin conjugated with AO remained even at a nearly isoelectric point. The improving effect of AO-conjugation on the characteristics of myosin was almost the same as Mf reacted with AO. Therefore, it is apparent that that improved functionalities of the glycosylated Mf reflect the functional changes of myosin.     

Pond farming of Nile tilapia, Oreochromis niloticus (L.), in northern Cameroon. Mixed culture of large tilapia (> 200 g) with cattle manure and cottonseed cake as pond inputs, and African catfish, Clarias gariepinus (Burchell), as police-fish

An experiment was conducted with tilapia-catfish polyculture at the Lagdo Fisheries Station in northern Cameroon. The objectives were: 1. To estimate the effect of supplementary cottonseed cake on net pond production in ponds already receiving dried cattle manure as basic treatment: and 2. To study the performance of African catfish, Clarias gariepinus (Burchell). in recruitment control of Nile tilapia, Oreochromis niloticus (L.). Recruitment control is essential in obtaining large tilapia sizes demanded in the market. Cottonseed cake, the most important agricultural by-product in the region, is expensive. Dried cattle manure may be collected free from corrals deserted by pastoral ethnic groups. Three treatments were tested in duplo in six earthen ponds of 525 m² each; treatment A. daily application of dried cattle manure only (266 kg ha^?1 day^?1); treatment B, daily manure + cottonseed at a nominal daily rate of 3% of tilapia biomass: treatment C, daily manure + cottonseed cake at 6% of tilapia biomass. Stocking densities per pond were 250 male Nile tilapia (mean W_o 222 g), 150 female tilapia (W₀= 202 g), 30 ‘large’ African catfish (W_o= 198 g); and 30 ‘small’ catfish (W₀= 52 g). Mean fish densities were 0.76 tilapia m^?2 and 0.11 catfish m^?2. Application of dried manure and cottonseed cake was 6 days per week, and the culture period was 100 days. Fish were sampled every month and feeding rates were adjusted accordingly. Dissolved oxygen content and algal turbidity (Secchi disc) were measured once a week. Extrapolated net pond productions, including recruits, were: -0.41 ha^?1 year^?1 (treatment A); 4.8 t ha^?1 year^?1 (treatment B) and 6.5 t ha^?1 year^?1 (treatment C). Differences between treatments B and C were not significant(P < 0.05). Fertilization with dried cattle manure only (zero cottonseed cake) led to a negative net pond production in treatment A (negative net tilapia production but slightly positive net catfish production). Dried manure at the given application rate did not contribute sufficient nutrients to maintain the stocked fish biomass via enhanced natural production, while pond biomass was high for such an extensive system (manure only). Best fish growth was observed in treatment C (male tilapia, 0.9 gday^?1: large catfish, 6.9 g day^?1) although differences between treatments B and C were not significant. Growth of male and female was not significantly different, but growth rates of tilapia and catfish were significantly different (P & lt; 0.05). Average yields of tilapia recruits in treatment B (1539 kg ha^?1 year^?1) and C (1829 kg ha^?1year^?1) were about four times the average yield of recruits in treatment A (468 kg ha^?1 year^?1) but differences between treatments A, B and C were not significant. It was sugcess, or the reproductive efficiency of tilapia in treatment A could have been lower as a result of that treatment. However, clouds of up-swimming fry appeared to be at least as numerous in the replicate ponds of treatment A as in the ponds of treatments B and C.     

POLYCULTURE OF CHANNEL CATFISH (Ictalurus punctatus) WITH ALL-MALE TILAPIA HYBRID

Channel catfish (Ictalurus punctatus) (x? = 0.8 g) and all-male hybrid tilapia fingerlings (Sarotherodon mossambica ♂ × S. hornorum ♀) (x? = 35.0 g) were stocked in 0.04 ha replicated ponds in Baton Rouge, Louisiana, in March and July 1981, respectively. The ponds were stocked at densities of 11,110 catfish per ha, 11,110 catfish with 5,550 tilapia per ha, 7,400 catfish per ha, and 7,400 catfish with 3,700 tilapia per ha. The fish were fed daily at 4% of estimated catfish biomass and were harvested in November 1981. There were no differences in dissolved oxygen or water temperature among the four culture systems (P > 0.05). The presence of tilapia, however, significantly increased water turbidity, pH and chlorophyll a concentrations (P < 0.05). Tilapia did not improve water quality and may have deteriorated it. Tilapia did not affect channel catfish growth or production (P > 0.05), but the presence of tilapia did significantly increase total fish yield (P < 0.05) by 13.5 and 32.2% at low and high catfish densities, respectively. Channel catfish and tilapia averaged 390 and 245 g at harvest, respectively. Overall catfish survival averaged 61%. Tilapia survival was 72% and 61% at low and high densities, respectively.     

Effect of shrimp head protein hydrolysates on the state of water and denaturation of fish myofibrils during dehydration

ABSTRACT:   To utilize fisheries waste products as food materials with functional properties, shrimp head protein hydrolysates (SHPH) from three species of shrimp, that is, Northern pink shrimp ( Pandalus eous ), Endeavour shrimp ( Metapenaeus endeavouri ) and Black tiger shrimp ( Penaeus monodon ), were produced by enzymatic hydrolysis using endopeptidase derived from Bacillus subtilis and exopeptidase derived from Aspergillus oryzae at a level of 0.1% (w/w). SHPH were rich in protein (90–91%) and amino acids (71–84%) but little fat (0.01–0.02%). The average molecular weight of SHPH was 300–1400. The effect of 5% SHPH (dry basis) addition on the state of water and denaturation of lizard fish myofibrils (Mf) during the dehydration process was evaluated by the desorption isotherm and the Ca-ATPase activity, and compared with the effect of sodium glutamate (Na-Glu). SHPH decreased the water activity and the Ca-ATPase inactivation, and increased monolayer sorbed water and multilayer sorbed water of Mf, although these effects of SHPH were smaller than those of Na-Glu. These findings suggest that the SHPH suppressed dehydration-induced denaturation of myofibrillar protein by stabilizing the hydrated water surrounding myofibrils.