木醋杆菌流加静置培养生产细菌纤维素

木醋杆菌在传统的分批静置培养方式下产生的细菌纤维素具有良好的成膜性,但难于实现工业化生产,为了解决这个问题,对传统的静置培养装置进行改造,形成流加静置培养方式,能够将静置培养与动态培养的优点结合起来。对分批静置和流加静置2种培养方式进行比较,结果表明,流加培养时,细菌纤维素产量达到11.7g/L,其产量是分批培养的3.44倍,反应器的效率为0.585 g/(L·d),高于分批培养的0.425 g/(L·d)。流加培养条件下细菌纤维素产量和反应器效率得到提高,主要是由于在整个培养过程中营养供给充足,促进木醋杆菌的生长,使糖转化率及细菌平均比生长速率都达到较高水平,大量转化和合成细菌纤维素。     

Direct measurement of oxygen concentration inside cultured cartilage for relating to spatial growth of rabbit chondrocytes

In static culture of rabbit chondrocytes in collagen gel, the direct measurement of dissolved oxygen (DO) concentration revealed that the DO level at the top surface of gel decreased due to an increase in overall cell density with elapsed time. The local cell density at the top surface on day 21 was 5.7 × 10⁷ cells/cm³, being 11 times that at the bottom of gel. This heterogeneity of cell distribution in the gel was considered to occur by limitation of oxygen supply into a deeper part of the gel. In shaking culture using a dish with gas-permeable film, the DO level was enhanced inside the gel and the overall cell density in the gel was achieved to be 2.9 times that in the static culture.     

富硒红发夫酵母补料分批培养研究

通过摇床培养实验,研究了红发夫酵母富硒培养的适宜糖浓度和C/N比;通过5L磁力搅拌发酵罐实验,探讨了在第8～32h之间分四次、七次和连续补料分批培养对细胞产量、细胞色素含量和硒含量的影响;结果表明,30.0g/L的葡萄糖浓度、C/N=2.7分别是分批培养时适宜的糖浓度和碳氮比,细胞产量、细胞色素含量和硒含量分别为14.2g/L、589.7、584.2μg/g;与摇床培养相比较,磁力搅拌发酵罐中补料分批培养显著地提高了细胞产量、细胞色素含量和硒含量;在补料培养中,连续补料的结果优于七次补料,七次补料优于四次补料;在10L机械搅拌罐中连续补料培养时,富硒红发夫酵母的细胞产量、色素含量和硒含量分别为26.7、764.3μg/g和1012.5μg/g。。     

Microbiological quality of bulk tank raw milk in Prince Edward Island dairy herds

The objectives of this study were to evaluate microbiological quality of bulk tank milk in Prince Edward Island, to evaluate correlation among milk quality criteria, and to determine seasonal effects on milk quality parameters. Bulk tank raw milk quality was evaluated on all Prince Edward Island dairy herds (n = 235) over a 2-yr period (March 2005 to March 2007). Biweekly total aerobic (TAC), preliminary incubation (PIC), laboratory pasteurization, and coliform (CC) counts were determined using a Petrifilm culture system. Additionally, bulk tank somatic cell count was determined weekly. The mean and median values were 12.8 × 10³ and 4.9 × 10³ cfu/mL for TAC, 29.6 × 10³ and 13 × 10³ cfu/mL for PIC, 87 and 12 cfu/mL for laboratory pasteurization count, 21 and 5 cfu/mL for CC, and 218 × 10³ and 187 × 10³ cells/mL for somatic cell count. There was moderate correlation (0.57) between TAC and PIC. All other correlation coefficients were low (<0.26). Correlation results suggest that a single quality parameter could not predict others used in this study. Seasonal data indicate that 1) in general, all counts tended to be low in winter, 2) the CC and somatic cell count were always high in summer, and 3) TAC tended to be high during summer.     

Protection of Lactobacillus acidophilus from bile salts in a model intestinal juice by incorporation into the inner-water phase of a W/O/W emulsion

Lactic acid bacteria have been paid increasing attention as a probiotics, but their viability is affected by the various digestive processes of their host such as the acidic stomach solution and bile acids. The protection of Lactobacillus acidophilus JCM 1132 against the cytotoxic bile acids was examined by incorporating the bacteria in the inner-water phase of a W/O/W emulsion. Sodium glycodeoxycholate and sodium glycochenodeoxycholate (6 mmol/l each) significantly decreased the cell viability from 5.2×10⁶ cfu/ml to 4.0×10³ and 1.3×10² cfu/ml, respectively, when the bacteria were directly dispersed in the solutions at pH 7 for 2 h. However, their incorporation in the inner-water phase of the W/O/W emulsion improved the viabilities to 1.6×10⁶ and 2.3×10⁴ cfu/ml, respectively. This improvement was ascribed to the inclusion of the bacteria in the emulsion because the viability of the bacteria, which were dispersed with the emulsion containing no bacteria in the solution, was very low. Although sodium deoxycholate decreased the viability of the cells included in the W/O/W emulsion, the inclusion significantly improved the cell viability against primary and secondary bile acids.     

An economic evaluation of freeze-dried kefir starter culture production using whey

An economic study is presented in which industrial-scale production of freeze-dried kefir starter culture is discussed based on results on a laboratory scale. Industrial scale-up was based on a 3-step process using 3 bioreactors of 100, 3,000, and 30,000 L for 300 kg of freeze-dried culture/d of plant capacity. The major cost component of the total investment was the freeze-drying machinery, which consisted of 57% of the total investment. Production cost was reduced from €15.4/kg ($18.5/kg) to ∉2.9/kg ($3.5/kg) when the production capacity was increased from 30 to 900 kg/d. An economic analysis revealed a 3.5-fold increase in production cost compared with the corresponding production cost of the wet product, with an added value of up to ∉10.8 × 10⁹ ($13.0 × 10⁹) within the European Union.     

Isoflavonoid production by soy plant callus suspension culture

Production of aglycone type isoflavonoids, Genistein and Daidzein, and β-glycosidic type isoflavonoids, Genistin and Daidzin, by the soy plant callus suspension culture was investigated in a batch system. Genistein and Daidzein concentrations increased during the exponential growth phase of the biomass. Genistin and Daidzin concentrations were not directly related with biomass production. Methyl jasmonate addition to the growth medium (0.1 kg/m³) was found to increase isoflavonoid biosynthesis by 5-6 times. Isoflavonoid production in the 7 days old culture increased with pulsed electric field (PEF) application at 1.6 kV, and aglycone forms were influenced to a greater extent.     

Temperature-dependent diffusion coefficient of oil from different sunflower seeds during extraction with hexane

Oil extraction from confectionery, oilseed and wild sunflower seeds with n-hexane was investigated by laboratory tests carried out in a stirred batch extractor at several temperatures (40, 50 and 60 °C). The rates of extraction were determined from ground sunflower seeds (particle sizes between 0.420 and 1.000 mm). The oil yield in the extract increased with higher contact time and extraction temperature in all the cases. Equilibrium constants at 50 °C for different solvent-ground seed ratios are reported. A mathematical model of oil extraction from seeds of sunflowers, based on a modified diffusive process in spherical geometry of particles, was proposed. The analysis of significance of the coefficient of fitting regression models showed significant differences between temperatures for each genotype and between genotypes at each temperature. The resulting diffusion coefficient ranged from 1.34 × 10⁻¹² to 1.87 × 10⁻¹² m²/s for confectionery, 2.06 × 10⁻¹² to 5.03 × 10⁻¹² m²/s for oilseed, and 9.06 × 10⁻¹³ to 1.18 × 10⁻¹² m²/s for wild sunflower. The temperature dependence of the diffusion coefficient was represented by an Arrhenius-type equation for each sunflower seed studied. Activation energy values of 13.74, 33.95 and 11.32 kJ/mol were obtained for confectionery, oilseed and wild sunflower, respectively.     

Efficient production of an antibody Fab fragment using the baculovirus–insect cell system

The production of an Fab fragment of the catalytic antibody 6D9 in lepidopteran insect cells infected with a recombinant baculovirus that contained both the heavy chain (Hc) and light chain (Lc) genes of the Fab fragment was investigated. Western blotting and enzyme-linked immunosorbent assay (ELISA) of culture supernatant showed that baculovirus-infected Trichoplusia ni BTI-TN-5B1-4 (High Five) cells secreted an Fab fragment that retained antigen-binding activity. Infection of High Five cells with a recombinant baculovirus, in which the Lc and Hc genes were located downstream of the baculovirus p10 and polyhedrin promoters, respectively, produced a higher Fab fragment yield than that obtained with a baculovirus in which the Hc and Lc genes were downstream of the p10 and polyhedrin promoters, respectively. Baculovirus-infected High Five cells secreted more of the Fab fragment than Spodoptera frugiperda Sf9 cells. Moreover, use of the baculovirus gp64 signal sequence upstream of the Lc and Hc genes resulted in greater yield of the secreted Fab fragment than use of the insect-derived BiP and melittin signal sequences. Consequently, the Fab fragment was obtained in a high yield (> 600 μg/ml) in a shake-flask culture of High Five cells infected at a multiplicity of infection (MOI) of 10 plaque-forming units (pfu)/cell with the recombinant baculovirus in which the Lc and Hc genes with the gp64 signal sequence were expressed under the control of the p10 and polyhedrin promoters, respectively. These results indicate that the baculovirus–insect cell system may allow efficient production of antibody Fab fragments.     

Growth and differentiation potentials in confluent state of culture of human skeletal muscle myoblasts

The transitional behaviors of myoblasts toward differentiation were investigated in the cultures at the low and high seeding densities (respectively, X₀ = 1.0 × 10³ and 2.0 × 10⁵ cells/cm²). In the culture at the low seeding density, an increase in confluence degree accompanied a decrease in growth potential (R_p), being R_p = 0.85 and 0.11 at t = 48 and 672 h, respectively. Myoblasts seeded at the high density resulted in the immediate cessation of growth with keeping the low range of R_p = 0.02–0.09 throughout the culture. The reduction of R_p led to the generation of three subpopulations of cells in proliferative, quiescent and differentiated states. Close cell contacts in the confluent state of high seeding culture induced cell quiescence to a higher extent with suppressing differentiation.     

The Influence of Debaryomyces hansenii, Candida deformans and Candida zeylanoides on the aroma formation of dry-cured “lacón”

The volatile profile of dry-cured “lacón” that has been inoculated with three different yeasts were determined and compared with a non-inoculated dry-cured “lacón”. Yeasts (Debaryomyces hansenii, Candida deformans and Candida zeylanoides) that were used as starter cultures in the present study were selected among yeasts that were isolated from native dry-cured “lacón” at different stages of ripening process. These starters were spread on dry-cured “lacón” surface in order to test their capacity to contribute on the generation of volatile compounds. A total of forty two volatile compounds were detected by dynamic headspace sampling followed by gas chromatography–mass spectrometry analysis. Significant differences (P < 0.001) on the volatile profiles of different batches were found in comparison with non-inoculated samples, showing the highest total area values for the inoculated ones. Esters were the most abundant chemical family in all batches studied except for C. zeylanoides batch, which showed greater amount of hydrocarbons than esters. The second more abundant family was hydrocarbons for control and C. deformans batches (147.6 and 445.24 × 10⁶ area units, respectively), alcohols for D. hansenii (363.77 × 10⁶ area units) and esters for C. zeylanoides (248.33 × 10⁶ area units). However, the aldehyde compound group in control batch samples was found to be significantly higher than in the inoculated ones (P < 0.001). Among inoculated batches, D. hansenii batch showed the lowest hexanal content (14.42 × 10⁶ area units) in comparison with non-inoculated batch (105.99 × 10⁶ area units). Among all batches studied, D. hansenii batch presented the highest area values for esters, alcohols, linear hydrocarbons, ketones, acids and furans; control batch for aldehydes and C. zeylanoides batch for branched hydrocarbons. Therefore, the study showed that every yeast strain produced a specific volatile profile which was also different from that of the control dry-cured “lacón”.     

Effects of the addition of direct-fed microbials and glycerol to the diet of lactating dairy cows on milk yield and apparent efficiency of yield

A study was conducted to evaluate the effects of a direct-fed microbial (M) and dietary glycerol (G) on milk yield, efficiency of yield, and nutrient digestibility during hot weather. Sixty Holstein cows averaging 120 d in milk (DIM) and 36.2 kg/d of milk were used in a 12-wk 2 × 2 factorial design trial from June through September 2008. Cows were fed a common diet during the 2-wk standardization period and were blocked by milk yield, DIM, parity, and dry matter intake. Diets were based on corn and ryegrass silages and balanced to be isocaloric and isonitrogenous. Treatments included a negative control (M− or G−), 4 × 10⁹ cfu/head of a combination of Lactobacillus acidophilus NP51 and Propionibacterium freudenreichii NP24 (M+), control plus 400 g/h per day of 99% pure food-grade glycerol (G+), and 4 × 10⁹ cfu/h per day of a combination of Lactobacillus acidophilus NP51 and Propionibacterium freudenreichii NP24 plus 400 g/h per day of 99% pure food-grade glycerol (MG++). No interactions were observed between direct-fed microbials and dietary glycerol in the study except on apparent nutrient digestibility. No differences were observed in dry matter intake, which averaged 22.7, 23.1, 23.4, and 22.9 for M−, G−, M+, and G+, respectively. Milk yield was increased for M+ compared with M− at 34.1 and 31.7 kg/d, but G+ had no effect on yield. No treatment effect was noted for milk fat percentage or milk protein percentage among diets. Milk protein yield was higher for M+ compared with M− at 0.93 versus 0.87 kg/d. Energy-corrected milk was improved for the M+ versus M− groups at 33.5 and 31.6 kg/d, respectively. No differences in respiratory rate, skin temperature, body temperature, or concentrations of serum glucose or urea N were observed among treatments. Improvement in apparent digestibility was observed with M+ and G+ compared with M−/G− in this experiment. The addition of a direct-fed microbial alone improved milk and protein yield, energy-corrected milk, and apparent digestibility of crude protein, neutral detergent fiber, and acid detergent fiber, and the inclusion of glycerol (G+) had a positive effect on apparent dry matter and acid detergent fiber digestibility compared with M−/G−. The addition of a direct-fed microbial and dietary glycerol may improve yield and digestibility for cows subject to heat stress.     

Effect of microencapsulation and resistant starch on the probiotic survival and sensory properties of synbiotic ice cream

Two types of synbiotic ice cream containing 1% of resistant starch with free and encapsulated Lactobacillus casei (Lc-01) and Bifidobacterium lactis (Bb-12) were manufactured. The survival of L. casei and B. lactis were monitored during the product’s storage for 180 days at −20 °C. The viable cell number of L. casei and B. lactis in the free state in prepared ice cream mixture was 5.1 × 10⁹ and 4.1 × 10⁹ CFU/mL at day one and after 180 days storage at −20 °C, these numbers were decreased to 4.2 × 10⁶ and 1.1 × 10⁷ CFU/mL, respectively. When we encapsulated the mentioned probiotic bacteria in calcium alginate beads, the probiotic survival raised at rate of 30% during the same period of storage at same temperature. In general, the results indicated that encapsulation can significantly increase the survival rate of probiotic bacteria in ice cream over an extended shelf-life. The addition of encapsulated probiotics had no significant effect on the sensory properties of non-fermented ice cream in which we used the resistant starch as prebiotic compound.     

Aqueous extraction of anthocyanins from Hibiscus sabdariffa: Experimental kinetics and modeling

Solid-liquid extraction of anthocyanins from calyces of Hibiscus sabdariffa L. was studied to evaluate the influence of the operating parameters. Solid-to-solvent ratio and particle size had the main impact on anthocyanin extraction efficiency. Maximum yield of anthocyanins (88%) was obtained at 25 °C with the highest solid-to-solvent ratio (1/25). The decrease in the particle size of the calyces from 2 cm to 150 μm drastically reduced the extraction time. The increase of temperature reduced the extraction time by increasing the diffusion coefficient (3.9 × 10⁻¹¹-1.35 × 10⁻¹⁰ m² s⁻¹ between 25 and 90 °C) but did not modify the extraction yield. A simple extraction model that integrated anthocyanin thermo-degradation kinetic was proposed. A good agreement between the predicted results of the models and experimental data was demonstrated. From a solid-to-solvent ratio of 1/5, an extraction yield of 63% and an anthocyanin concentration of 0.3 g L⁻¹ could be obtained in less than 10 min.     

产朊假丝酵母核酸高产株的选育及其发酵性能研究

为了获得一株发酵性能优良的高核酸酵母,以产朊假丝酵母(Candida utilis)CL1501为出发菌株,采用紫外-亚硝基胍复合诱变,筛选获得一株高核酸含量的突变株CL15013,经测定其核酸含量占菌体干质量的16.8%,高于出发菌47.8%。对比研究其流加及分批培养工艺,流加培养细胞收获量为16.9 g/L,比分批培养提高94.3%;正交试验设计优化流加培养条件后,CL15013的收获量达21.3 g/L,比分批培养提高144.8%,具有良好的生产应用潜力。     

Mathematical model of the acute inflammatory response to Escherichia coli in intramammary challenge

We constructed a mathematical model of the early response to Escherichia coli infection of the mammary gland and explored the roles and interactions between inflammatory cells and bacteria. The model incorporates 3 equations that describe the interactions among bacteria, milk somatic cells, and blood leukocyte densities. These 3 equations were fitted to cell densities observed during acute inflammatory responses in unvaccinated and vaccinated heifers inoculated with 10⁴ or 10⁶ cfu of E. coli. The rates computed for the cellular transit from the storage sites to the blood and from the blood to the milk were lower in cows receiving 10⁴ cfu but increased at approximately 6 × 10⁻⁶ and 30 × 10⁻⁶ μL/cfu per h in nonvaccinated or vaccinated cows inoculated with 10⁶ cfu, respectively. The cellular rates of bacterial killing were highest in unvaccinated cows (∼400 × 10⁻⁶ μL/cell per h) when compared with vaccinated cows (200 to 300 × 10⁻⁶ μL/cell per h). A critical density of milk somatic cells at which bacteria density is constant was computed from the model at 2 × 10⁶ cells/mL, and a one-way sensitivity analysis revealed that the changes in milk cellular densities were mostly sensitive to variations in the rate of bacterial killing and in the rate of production of inflammatory cells.     

碳酸氢铵为氮源对螺旋藻培养的影响

以碳酸氢铵作为氮源,研究在分批培养及流加培养条件下其对螺旋藻生长的影响。结果表明：当培养液中碳酸氢铵浓度小于5mmol/L时,螺旋藻生长正常;碳酸氢铵浓度超过5mmol/L时,螺旋藻生长受到抑制,解体死亡。采用生物量反馈补料的流加策略可以使培养液中螺旋藻生物量达到3.08g/L,产率达到0.26g/(L ·d),藻体中蛋白质及叶绿素含量分别达到65.06%和13.37mg/g,结果证实了碳酸氢铵为氮源高密度培养螺旋藻的可行性。     

Chemical characterization and antioxidant activity of sulfated polysaccharide from the red seaweed Gracilaria birdiae

Hydrocolloids from seaweeds have interesting functional properties, such as antioxidant activity and gelling ability. A polysaccharide was isolated by aqueous extraction at 90 °C from the red seaweed Gracilaria birdiae (Gb), with a yield of 27.2% of the seaweed dry weight. The sulfate content of the polysaccharide was 8.4% and the main sugars present were galactose (65.4 mol%), 3,6-anhydrogalactose (25.1 mol%) and 6-O-methylgalactose (9.2 mol%). Gel permeation chromatography showed that Gb polysaccharide is a heterogeneous system, with molar mass at the main peak of 3.7 × 10⁵ g mol⁻¹ and a shoulder of 2.6 × 10⁶ g mol⁻¹. The sulfated polysaccharide of Gb characterized by FTIR exhibits the characteristic bands of agarocolloids (at 1375 and 770 cm⁻¹).     

碱性中和与补料分批高密度培养保加利亚乳杆菌的研究

本实验采用葡萄糖反馈抑制补料、调节发酵液pH 值、碱性中和与补料分批复合培养等方法对保加利亚乳杆菌高密度培养进行研究。研究表明,碱性中和与补料分批复合培养条件为：保加利亚乳杆菌培养18h 和26h 时,向培养液补加碳氮比为0.67 的补料液5ml,并且每隔1.5h 调节pH 值至6.5,培养36h,培养液中保加利亚乳杆菌菌体浓度最高达9.02 × 1011CFU/ml,菌体干重达14.266g/L。     

Holstein-Friesian strain and feed effects on milk production, body weight, and body condition score profiles in grazing dairy cows

Data from 113 lactations across 76 cows between the years 2002 to 2004 were used to determine the effect of strain of Holstein-Friesian (HF) dairy cow and concentrate supplementation on milk production, body weight (BW), and body condition score (BCS; 1 to 5 scale) lactation profiles. New Zealand (NZ) and North American (NA) HF cows were randomly allocated to 1 of 3 levels of concentrate supplementation [0, 3, or 6 kg of dry matter (DM)/cow per d] on a basal pasture diet. The Wilmink exponential model was fitted within lactation (Y_DIM = a + b e(^{−0.05 × DIM)} + c × DIM). The median variation explained by the function for milk yield was 86%, between 62 and 69% for milk composition, and 80 and 70% for BW and BCS, respectively. North American cows and cows supplemented with concentrates had greater peak and 270-d milk yield. Concentrate supplementation tended to accelerate the rate of incline to peak milk yield, but persistency of lactation was not affected by either strain of HF or concentrate supplementation. No significant strain by diet interaction was found for parameters reported. New Zealand cows reached nadir BCS 14 d earlier and lost less BW (22 kg) postcalving than NA cows. Concentrate supplementation reduced the postpartum interval to nadir BW and BCS, and incrementally increased nadir BCS. New Zealand cows gained significantly more BCS (i.e., 0.9 × 10⁻³ units/d more) postnadir than NA cows, and the rate of BCS replenishment increased linearly with concentrate supplementation from 0.5 × 10⁻³ at 0 kg of DM/d to 0.8 × 10⁻³ and 1.6 × 10⁻³ units/d at 3 and 6 kg of DM/d concentrates, respectively. Although there was no significant strain by diet interaction for parameters reported, there was a tendency for a strain by diet interaction in 270-d BCS, suggesting that the effect of concentrate supplementation on BCS gain was, at least partly, strain dependent.