Enzymatic Production of Ribonucleotides from Autolysates of Kluyveromyces marxianus Grown on Whey

After 20h fermentation of medium containing 5% (w/v) dehydrated whey, at 30°C, pH 4.5, yeast cells were harvested, diluted in 0.1M KH₂PO₄, and autolyzed at different pHs (6.5–7.5) and temperatures (45–55°C). Phosphodiesterase (0.2–1.0% w/v, 65°C, pH 6.5, 6h) and adenyl deaminase (0.5-1.0% w/v, 60°C, pH 5.5, 4h) were added to the autolysates. After heat treatment (100°C, 15 min), samples were analyzed by RP-HPLC and LC/MS. Production of 5′-ribonucleotides was maximized at 50°C, pH 6.5. Yields of 5′-AMP (800 μg/g of biomass) and 5′-GMP (2000 μg/g) increased considerably after addition of 1.0% phosphodiesterase. 5′-IMP increased only after addition of 1.0% adenyl deaminase.     

EFFECT OF DIETARY SORGHUM DISTILLERY RESIDUE ON HEMATOLOGICAL CHARACTERISTICS OF CULTURED GREY MULLET (MUGIL CEPHALUS)—AN ANIMAL MODEL FOR PRESCREENING ANTIOXIDANT AND BLOOD THINNING ACTIVITIES

The sorghum distillery residue (SDR) has been an underutilized by‐product with estimated production of 150 ton/day in Kinmen, Taiwan. The objective of this study was to test for any physiological effects of SDR, thus to utilize it as a nutraceutical feed ingredient in diets for cultured fish. Hot air‐dried, wet, and dehulled‐wet sorghum distillery residue showed 63%, 90% and 97% inhibition of the hemoglobin‐catalyzed oxidation of linoleic acid compared to soybean (13%) and rice bran (78%). The feed formulated with 20% wet or dehulled‐wet sorghum distillery residue both showed an antioxidant activity of 68% being higher than the control diet (53%). Feeding these diets to cultured grey mullet for 60 days in summer (temperature ranged 24–30C), resulted in a lower hydroperoxide content in gill tissue, as shown by a chemiluminesence intensity of 1806 or 1409 mV as opposed to 2666 mV for fish fed a control diet. In winter, when the water temperature decreased to 14C, grey mullet fed a diet consisting of 10% dehulled wet sorghum distillery residue had a blood viscosity of 1.9 mPas and a hematocrit value of 33%, in contrast to 3.6 mPas and 41% for control. The blood of the control group started to aggregate in 6 h and showed hemolysis, while the mullet fed dehulled, wet sorghum distillery residue did not show blood aggregation, maintained normal fluidity and erythrocyte membrane integrity. It seems that cultured fish may have the potential as an animal model for prescreening antioxidant and blood thinning effects of food ingredients.     

THE MOLECULAR WEIGHT OF α-AMYLASE INHIBITOR FROM WHITE BEAN cv 858B (PHASEOLUS VULGARIS L.) IS 56 kDa, NOT 20 kDa

The molecular weights (M_rs) of α-amylase inhibitors (αAIs)fiom 18 (Ah) bean cultivars estimated by Superose 12 gelfiltration chromatography were 22–62% smaller than those determined by Sephadex G-100 gel filtration and by polyacrylamide gel electrophoresis (PAGE) methods. αAI-4 from WKB cultivar 858B was purified and the Mr was shown to be 51.0 kDa based on Sephadex G-100 gel filtration chromatography and by PAGE. A M_r for aAI-4 of 56.714 kDa was determined by laser-assisted time-of-flight mass spectrometry and appears to be the true M_r of the mature glycosylated active aAI-4. The results show that Superose 12 gelfiltration chromatography is not usefulfor M_r determination of some proteins. Sodium dodecyl sulfate electrophoresis (SDS-PAGE) showed that the 56.7 kDa aAI-4 molecule dissociated into 45.0, 33.6,15.2 and 12.4 kDa submolecules, with only the two small subunits, a and β, present at high SDS concentration. This provides evidence that the aAI-4 molecules composition is α₂β².     

OCCURRENCE OF TRANSGLUTAMINASE IN GREY MULLET (MUGIL CEPHALUS) MUSCLE AND IT'S EFFECT ON MINCED FISH PRODUCT

The gel strength of the minced fish product made from the unwashed mullet mince was found higher than that of the washed product. Transglutaminase (TGase) was found in the water soluble fraction of mullet muscle. It's optimal temperature was at 30C to 35C and the optimal pH was 7.5 to 7.7. Increased setting time at 30C, increased the gel strength of the minced fish product produced from the unwashed mullet mince. p-Chloromercuribenzoate (PCMB), an inhibitor to TGase was added to the mullet mince up to 2.0 mM, the mince was set at 35C and then heated to 85C. The gel strength of the product was inversely correlated to the PCMB concentration, Y₁= - 0.45X + 1.66 (r = 0.95). Studies of setting of the mullet mince at temperatures ranging 20 to 60C indicated that maximal gel strength was obtained at 35C, coinciding with the optimal temperature of TGase. Meat from 21.5 monthold grey mullet produced a minced product of higher gel strength than those produced from younger fish, although the muscle TGase activities were not significantly different.     

Antioxidant Effects of Carnosine and Phytic Acid in a Model Beef System

Antioxidant and color stability effects of carnosine and phytate were compared in a fresh beef model system and in cooked beef. Both compounds increased the rate of pH decline in pre-rigor muscle. Phytate also increased the rate of post-mortem glycogen catabolism. Both antioxidants inhibited metmyoglobin formation in raw samples during storage. Phytate was more effective than carnosine for inhibition of lipid peroxidation. Heme iron content was negatively related to lipid peroxidation in cooked beef (r=–0.92). Phytate was also more effective for inhibition of iron release from heme during cooking. Phytate is recommended over carnosine as an effective antioxidant in cooked meats.     

Computed tomographic evaluation of gas hole formation and structural quality in Gouda‐type cheese

Computed tomography (CT) was performed on Gouda‐type cheese during ripening to evaluate gas hole formation and structural quality. The cheese was exposed to different ripening conditions, including variations in ripening temperature and concentration of butyric acid bacteria. Computed tomography images were obtained every 2 weeks for 16 weeks to assess the volume, shape and location of gas holes. The results demonstrate that CT makes the nondestructive monitoring of cheese gas hole formation and evaluation of the structural features of cheese possible throughout the ripening period.