Optimizing Skim Milk Yogurt Properties: Combined Impact of Trans-glutaminase and Protein-Glutaminase.

The lack of fat in yogurt can lead to alterations in taste and whey separation, reducing consumer acceptance. In this study, the feasibility of enhancing the quality of skim milk yogurt through a combination of transglutaminase (TG) and protein-glutaminase (PG) was investigated. The combination of TG and PG resulted in simultaneous cross-linking and deamidated of casein micelles, with PG deamidation taking priority over TG cross-linking, leading to higher solubility and lower turbidity of milk proteins compared with TG alone. When 0.06 U/mL TG and 0.03 U/mL PG were added, firmness and viscosity indexes significantly increased by 38.26 and 78.59%, respectively as compared with the control. Microscopic images revealed increased cross-linking with casein and filling of cavities by smaller sub-micelles in the combination of TG and PG treatment. Furthermore, the combination of TG and PG resolved issues of rough taste and whey separation, leading to improved overall liking. This study highlights the benefits of using both enzymes in dairy production and has important implication for future research.

Effects of elevated CO2, warming and precipitation change on plant growth, photosynthesis and peroxidation in dominant species from North China grassland.

Warming, watering and elevated atmospheric CO2-concentration effects have been extensively studied separately; however, their combined impact on plants is not well understood. In the current research, we examined plant growth and physiological responses of three dominant species from the Eurasian Steppe with different functional traits to a combination of elevated CO2, high temperature, and four simulated precipitation patterns. Elevated CO2 stimulated plant growth by 10.8-41.7 % for a C3 leguminous shrub, Caragana microphylla, and by 33.2-52.3 % for a C3 grass, Stipa grandis, across all temperature and watering treatments. Elevated CO2, however, did not affect plant biomass of a C4 grass, Cleistogenes squarrosa, under normal or increased precipitation, whereas a 20.0-69.7 % stimulation of growth occurred with elevated CO2 under drought conditions. Plant growth was enhanced in the C3 shrub and the C4 grass by warming under normal precipitation, but declined drastically with severe drought. The effects of elevated CO2 on leaf traits, biomass allocation and photosynthetic potential were remarkably species-dependent. Suppression of photosynthetic activity, and enhancement of cell peroxidation by a combination of warming and severe drought, were partly alleviated by elevated CO2. The relationships between plant functional traits and physiological activities and their responses to climate change were discussed. The present results suggested that the response to CO2 enrichment may strongly depend on the response of specific species under varying patterns of precipitation, with or without warming, highlighting that individual species and multifactor dependencies must be considered in a projection of terrestrial ecosystem response to climatic change.

Effects of Flammulina velutipes polysaccharide with ice recrystallization inhibition activity on the quality of beef patties during freeze-thaw cycles: An emphasis on water status and distribution.

The antifreeze activity of Flammulina velutipes polysaccharide (FVP) autoclave-extracted with dilute alkaline and effects of FVP on moisture status, size of ice crystals, physical and chemical characteristics of beef patties during repeated freeze-thaw (F-T) cycles were investigated. Results showed that FVP exhibited ice recrystallization inhibition activity and was able to alter the onset freezing/melting temperature of beef patties. 0.01% FVP significantly alleviated (P < 0.05) the decrement in water holding capacity by inhibiting water migration, restraining the mobility of water, and reducing the size of ice crystals of beef patties during the repeated F-T cycles. In addition, FVP could effectively inhibited oxidation reaction and protein aggregation of beef patties with significant decreases in TBARS value, protein turbidity, contents of total sulfhydryl and carbonyl of myofibrillar protein, and an increase in protein solubility during the repeated cycles. These results suggest FVP could be developed to be a promising cryoprotectant in frozen patties.

Effect of protein-glutaminase on the texture, rheology, microstructure and sensory properties of skimmed set-type yoghurt.

The effects of enzymatic deamidation by protein-glutaminase (PG) on the texture, rheology, microstructure, and sensory properties of skimmed set-type yoghurt were studied. The proportion of small-particle size milk protein micelles (10-50 nm) increased significantly from 0 to 99.39% after PG deamidation. Cryo-SEM results revealed that PG-treated yoghurt had a denser and less open 3D structure. PG was effective at inhibiting post-acidification during storage at 4 ℃. The water holding capacity of PG-treated yoghurt (0.12 U·mL-1) increased by more than 15%. The fluidity and viscosity of yoghurt were significantly improved with increasing PG dose. Sensory evaluation revealed that PG (0.06 U·mL-1) significantly improved the smoothness and creaminess of skimmed set-type yoghurt, which corresponded to the pastiness in texture. In summary, PG can effectively address the problems of post-acidification, gel fracture, and flavors change in skimmed set-type yoghurt, providing new applications for PG in the food industry.

Methionine biosynthesis pathway genes affect curdlan biosynthesis of Agrobacterium sp. CGMCC 11546 via energy regeneration.

Curdlan is a water-insoluble exopolysaccharide produced by Agrobacterium species under nitrogen starvation. The curdlan production in the ΔmdeA, ΔmetA, ΔmetH, and ΔmetZ mutants of methionine biosynthesis pathway of Agrobacterium sp. CGMCC 11546 were significantly impaired. Fermentation profiles of four mutants showed that the consumption of ammonia and sucrose was impaired. Transcriptome analysis of the ΔmetH and ΔmetZ mutants showed that numerous differentially expressed genes involved in the electron transfer chain (ETC) were significantly down-regulated, suggesting that methionine biosynthesis pathway affected the production of energy ATP during the curdlan biosynthesis. Furthermore, metabolomics analysis of the ΔmetH and ΔmetZ mutants showed that ADP and FAD were significantly accumulated, while acetyl-CoA was diminished, suggesting that the impaired curdlan production in the ΔmetH and ΔmetZ mutants might be caused by the insufficient supply of energy ATP. Finally, the addition of both dibasic sodium succinate as a substrate of FAD recycling and methionine significantly restored the curdlan production of four mutants. In conclusion, methionine biosynthesis pathway plays an important role in curdlan biosynthesis in Agrobacterium sp. CGMCC 11546, which affected the sufficient supply of energy ATP from the ETC during the curdlan biosynthesis.

Characterization and rheological properties analysis of the succinoglycan produced by a high-yield mutant of Rhizobium radiobacter ATCC 19358.

Succinoglycan is an industrially important exopolysaccharide biosynthesized by bacteria. In this study, mutant strain 18052 N-11 was obtained from the wild type strain Rhizobium radiobacter ATCC 19358 by NTG mutagenesis. It has a high yield succinoglycan of 32.5 g/L cultured in a 15 L-fementer for 72 h. Succinoglycan SG-A from the wild type strain has two components, and the molecular weights were 1.55 × 107 Da and 1.26 × 106 Da, respectively. While, succinoglycan SG-N from the mutant strain was a homogeneous polysaccharide, and the molecular weight was 1.01 × 107 Da. The molecular weight of both succinoglycan was higher than those reported in literatures. DSC thermogram of SG-A showed a higher endothermic peak than that of SG-N due to the higher crystallinity of SG-A. The dynamic frequency sweep test of SG-A and SG-N showed that the elastic modulus G' and viscosity modulus G" curves intersected at 65 °C, indicating the thermally induced order-disorder conformation. The results of effect of concentrations (2.5-15%) and temperatures (25-75 °C) on apparent viscosity of SG-A and SG-N showed that the succinoglycan solutions exhibited non-Newtonian, shear-thinning behavior. Both SG-A and SG-N showed an excellent emulsification activity. The characterizations and rheological properties make SG-A and SG-N prominent candidates in food, cosmetics, pharmaceutical and petroleum industries.

Glutamine synthetase gene glnA plays a vital role in curdlan biosynthesis of Agrobacterium sp. CGMCC 11546.

Curdlan is a neutral linear exopolysaccharide produced by Agrobacterium spp. under nitrogen-limiting conditions. In this study, we explored the role of glnA in curdlan biosynthesis in Agrobacterium sp. CGMCC 11546. The curdlan production of the ΔglnA strain was impaired, decreasing by 93% compared with that of the wild-type strain after 96 h fermentation. Analysis of fermentation profiles revealed that cell growth and utilization of carbon and nitrogen sources were impaired in the ΔglnA strain. Transcriptome analysis indicated that various of genes involved in curdlan biosynthesis were downregulated after 24 h fermentation in the ΔglnA strain, particularly genes involved in heme synthesis and the electron transport chain, which are essential for energy generation. Metabolomics analysis revealed flavin adenine dinucleotide (FAD) and adenosine diphosphate (ADP) accumulation in the ΔglnA strain, suggesting insufficient energy supply. Furthermore, glnA overexpression led to an 18% increase in the curdlan yield of the ΔglnA mutant compared with that of the wild-type strain after 96 h fermentation. Taken together, the findings demonstrate that glnA plays a vital role in curdlan biosynthesis by supplying ATP via regulating the expression of genes involved in heme synthesis and the electron transport chain.

Characterization and improvement of curdlan produced by a high-yield mutant of Agrobacterium sp. ATCC 31749 based on whole-genome analysis.

Curdlan is a bacterial, water-insoluble, linear homopolysaccharide that has been widely used in the food industry. In this study, genome information of strain CGMCC 11546, a UV-induced high-yield mutant of the model curdlan-producing strain Agrobacterium sp. ATCC 31749, was used to investigate the molecular mechanism of curdlan biosynthesis. The maximum curdlan yield of 47.97 ± 0.57 g/L was obtained from strain CGMCC 11546 by using optimal media containing 60 g/L sucrose, 6 g/L yeast, 2 g/L KH2PO4, 0.4 g/L MgSO4·7H2O, 2 g/L CaCO3, 0.1 g/L FeSO4·7H2O, 0.04 g/L MnSO4, and 0.02 g/L ZnCl2 at 30 °C and 280 rpm after 96 h of fermentation. The gel strength of curdlan was improved by 41 % by knocking out the ß-1,3-glucanase genes exoK and exsH of strain CGMCC 11546. Furthermore, the application of curdlan from the ΔexoK-exsH strain in noodles significantly improved the eating quality of both raw and cooked noodles.

Comparison of bacterial nanocellulose produced by different strains under static and agitated culture conditions.

Bacterial nanocellulose (BNC) has many advantages over plant cellulose, which make it widely used in many fields, especially in the food industry. In this study, three strains including BCA263, BCC529, and P1 were selected for characteristics analysis of BNCs under static and agitated culture conditions. The BNCs produced under static culture condition were in the shape of uniform membrane, while BNCs produced under agitated culture were in form of small agglomerates and fragments. BCA263 and BCC529 strains were more suitable for static culture, while P1 strain was more suitable for agitated culture. BNCs produced under static culture condition exhibited higher crystallinity, stronger tensile strength, denser network structure, higher temperature resistance and good flame retardancy; while BNCs produced under agitated culture condition exhibited larger porous and lower crystallinity. Furthermore, BNCs produced under agitated culture condition were more suitable as a stabilizer of coffee milk beverage.

Growth responses of Picea mongolica seedlings to defoliation rate.

Picea mongolica W. D. Xu. is an endemic species in China. The spruce forest is only found in semi-arid habitat in Inner Mongolia Autonomous Region of China. Based on the simulative defoliation experiment, it was proved that Picea mongolica seedlings had the compensatory and overcompensatory effects under the certain defoliation rate. The results of variance analysis on growth indexes showed that in PM I (natural regeneration seedlings under Picea mongolica forest), the differences of H1 (height in June 23) and H2 (height in September 3) were extremely significant, and the difference of D(diameter at the breast height) were not significant. In PM II (artificial regeneration seedlings under Betula platyphylla Suk. forest), the difference of H1 was significant, the difference of H2 was not significant, and the difference of D was extremely significant. The regression equations were established and the compensatory and overcompensatory points were obtained. In PM I, the compensatory points of H1, H2, and D were 0.7628, 0.7436, 0.5725, and the overcompensatory points were 0.6056, 0.5802 and 0.2909 respectively. In PM II, the compensatory points of H,, H2, and D are 0.5012, 0.3421, 0.2488, and the overcompensatory points are 0.4137, 0.2633 and 0.0747 respectively. These results suggested that the induction of compensatory growth mechanisms in spruce seedlings required a threshold level of defoliation, and the insects in Picea mongolica forest could be controlled in a certain degree.

Recent trends in nitrogen flows with urbanization in the Shanghai megacity and the effects on the water environment.

The objectives of this study are to diagnose and prevent environmental problems that threaten urban sustainability, the impact of changes in lifestyle (diet, domestic sanitation, and motorization), and production style (agriculture, industry, and services) with the rapid urbanization on regional nitrogen (N) flows, and the water environment was quantitatively evaluated. The megacity Shanghai was chosen as a case study to investigate the temporal changes in nitrogen flow during 1980-2008 by a multidisciplinary approach (a field survey, a regional nitrogen mass balance model, input-output analysis, etc.). Although the total potential nitrogen load in Shanghai has decreased in the 2000s and water pollution problems seem to have improved, the problem has shifted and expanded to affect a wider area through the food/product chain and water/air movement. Further effective solutions that aim at material cycles are necessary and have to be implemented on a large scale.

Impact assessment of human diet changes with rapid urbanization on regional nitrogen and phosphorus flows--a case study of the megacity Shanghai.

Regional material flows are strongly influenced by human diets. To diagnose and prevent environmental problems that threaten urban sustainability, the impact of human diet changes with rapid urbanization on the regional nitrogen (N) and phosphorus (P) flows were quantitatively evaluated. A survey of day-to-day activities was conducted of 450 individuals surveyed (adults over 18 years old) in three representative areas (the central district, the new district, and the suburban/rural areas) of Shanghai, a megacity which has attracted worldwide attention. The lifestyle (eating habits, domestic sanitation, drainage facilities, etc.) pattern was determined and the potential N and P loads from human diets on the environment were calculated. The daily potential nitrogen and phosphorus loads from human diets was 19.36 g-N, 1.80 g-P in the central district, 16.48 g-N, 1.52 g-P in the new district, and 13.04 g-N, 1.20 g-P in the suburban/rural areas of Shanghai. Respondents in all three areas, especially those in the suburban/rural areas reported a preference for increasing the intake of animal-derived as well as processed foods, which means that the potential N and P load from human diets to the environment will increase further. In addition, most respondents consider industrial wastewater discharge as the main cause of eutrophication of waterbodies, though in recent years water pollution caused by domestic wastewater has increased rapidly, but this has received much less attention. Environment-friendly eating habits and improvements in the environmental awareness will be required.

[Effects of elevated CO2 concentration on rhizosphere soil microbes under Pinus koraiensis and Pinus sylvestriformis seedlings].

The study showed that under Pinus sylvestriformis seedlings, the amount of rhizosphere soil bacteria, but not fungi and actinomyces, increased significantly (P < or = 0. 001) with CO2 enrichment (700 and 500 micromol x mol(-1)), and the same (P < or = 0.001) was under Pinus koraiensis seedlings, with the exceptions of 700 micromol CO2 x mol(-1) in August and 500 micromol CO2 x mol(-1) in July, compared to the ambient chamber and the ambient in each month. No significant effect of elevated CO2 was found on the amount of rhizosphere soil fungi except in September ( P < or = 0.001), and the response of actinomyces to elevated CO2 was also insignificant.

[Ecological carrying capacity and Chongming Island's ecological construction].

This paper overviewed the goals of Chongming Island's ecological construction and its background, analyzed the current eco-economic status and constraints of the Island, and put forward some scientific issues on its ecological construction. It was suggested that for the resources-saving and sustainable development of the Island, the researches on its ecological construction should be based on its ecological carrying capacity, fully take the regional characteristics into consideration, and refer the successful development modes at home and abroad. The carrying capacity study should ground on systemic and dynamic views, give a thorough evaluation of the Island's present carrying capacity, simulate its possible changes, and forecast its demands and risks. Operable countermeasures to promote the Island's carrying capacity should be worked out, new industry structure, population scale, and optimized distribution projects conforming to regional carrying capacity should be formulated, and effective ecological security alarming and control system should be built, with the aim of providing suggestions and strategic evidences for the decision-making of economic development and sustainable environmental resources use of the region.

[Key problems in ecological research on vegetations in Northeast China].

There exist many controversial problems in ecological research on vegetations in Northeast China, in spite of systemic studies for half century. In this paper, some comments were put forward on the recent researches of our concerned problems: 1) The zonal distribution pattern of vegetations in Northeast China could be quantificationally explained according to Kira's warmth index (WI), coldness index (CI), and Xu Wenduo's humidity index (HI). 2) There exists tundra vegetation in the north of Daxinganling Mountains with 1400 m altitude and above, which is the third tundra in China found by us firstly in 1963, and its WI < 15 degrees C x month. 3) The vegetation boundary between Daxinganling and Xiaoxinganling Mountains is one of the first class lines in vegetation sub-area. It locates in Aihui-Guosonggou-the Nen River, and the WI here is 45 degrees C x month. 4) In Daxinganling Mountains, the vegetation has significant zonal differentiation. In the south, the vegetation is typical steppe; in the middle, the vegetation is forest-steppe; and in the north, the vegetation is boreal coniferous forest. The HI here are 3.5-5.5, 5.5-7.5, and > 7.5 mm/degree C x month, respectively. The broadleaved forest in the east of Daxinganling Mountains is the forest vegetation type in forest-steppe zone. 5) In the eastern mountains of Northeast China, Betula ermanii forest is an important composition of vegetation vertical zone in mountains, and it is the timberline. The forest (WI is 20-15 degrees C x month) is the zonal vegetation type, whereas the forest (WI > 20 degrees C x month) is the non-zonal vegetation type. 6) In Hunshandake Sandy Land in Inner Mongolia Autonomous Region, spruce forest is the peculiar forest ecosystem type in continent, but which composition the spruce species belongs to is a controversial problem in plant class in China for a long time. It is proved further that it is a new species, namely, Picea mongolica (H. Q. Wu) W. D. Xu, cmb. nov.-Picea meyeri Rehd. et Wils var. mongolica (H. Q. Wu), according to the karyotype analysis and isozyme experiment.

[Position of Betula ermanii population ecotone in Changbai Mountains].

The vegetation on the northern slope of Changbai Mountains forms a vertical zone due to the vertical differentiation of moisture and heat conditions. Ecotones are obviously existed between different vegetation zones, but it is difficult to decide their positions. In the area from 1400 m to 2200 m elevation, we adopted the methods of gradient sampling, fractal analysis, population pattern analysis, and interspecific competition index analysis to describe Betula ermanii population ecotone. The results showed that there was a forest ecotone between Betula ermanii and Picea-Abies forest near elevation 1650 m, and there was a forest line ecotone between Betula ermanii and alpine tundra near elevation 2080 m.

[Geostatistical analysis of the pattern of Betula ermanii population in Changbai Mountain].

The distribution pattern and spatial correlation of Betula ermanii population in Changbai Mountain were studied using the theory of geostatistics. According to the data, these mivariograms of Betula ermanii volume were calculated, the models of semivariograms were simulated, and Kriging interpolation was also done to draw the Kriging map. The results showed that at the elevation of 1650-1700 m, the semivariograms of Betula ermanii volume could be described as spherical model, the spatial distribution pattern was the aggregated type, and the population was in a trend of declining. At the elevation of 1750-2000 m, the semivariograms of Betula ermanii volume could be described as linear model, the spatial distribution pattern was the random type, the population was stable. At the elevation of 2000-2150 m, the semivariograms of Betula ermanii volume could be described as spherical model, the spatial distribution pattern was the aggregated type, and the population was in a tend of increasing. Betula ermanii population in Changbai Mountain was in a trend of moving upper, especially Betula ermanii population in the ecotone.

[Gradient distribution of soil N, P, and K along the distance from Picea mongolica seedlings root surface].

Six years old seedlings of Picea mongolica were planted in pots with horizontal and vertical root treatments. Soil samples were stratified collected, and their available nitrogen (N), phosphorus (P), and potassium (K) contents were determined. The results showed that the available contents of N, P and K in soils along the distance from Picea mongolica seedlings root surface had a special gradient distribution. Near root surface, there was a depletion zone of soil available N, P, and K, and along the distance from it, the nutrient element contents increased gradually and reached their background values in the bulk soil. In the horizontal root treatment, the depletion zone of soil available N, P, and K existed in different distance from root surface, owing to the absorption and the use intensity of the seedlings to these nutrient elements. The depletion zone of soil available N and K appeared from 1 cm from root surface, and that of available P existed in 0.5 cm from root surface. In the vertical root treatment the depletion zone of available N and K also appeared from 1 cm from root surface as in the horizontal root treatment, but the available P content near root surface was lower than that far away from root surface. It is proved that the absorption and the utilize intensity of soil available P by Picea mongolica seedlings was intense, which might become a limiting factor to its growth and development. Therefore, Picea mongolica should be planted on soils rich in phosphorus, or P and N fertilizers should be applied to improve the absorption and the use efficiency of available P by Picea mongolica.

[Eco-physiological responses of Picea mongolica ecotypes to drought stress].

The seedlings of different Picea mongolica ecotypes were treated with drought stress, and their height growth, MDA, proline, and chlorophyll content were investigated. The results showed that the height growth was obviously reduced by drought stress. With sufficient water supply, the height growth of f. viridis W. D. Xu f. nov Picea mongolica was rapid and obviously better than that of f. purpurea W. D. Xu f. nov Picea mongolica, but was obviously reduced by intense drought stress. Furthermore, drought stress shortened the annual growth period of Picea mongolica, and made its terminal bud formation more than one month earlier increased in both needles and roots, but was higher in needle than in root. The MDA content was higher in Picea mongolica than in f. viridis W. D. Xu f. nov Piburcea mongolica, and the proline content in needles was increased with increasing drought stress, but in roots, the proline content was higher in f. viridis W. D. Xu f. nov Picea mongolica than in f. purpurea W. D. Xu f. nov Picea mongolica and f. rubra W. D. Xu f. nov Picea mongolica. The latter 2 forms showed a similar trend in chlorophyll content. Their chlorophyll a, chlorophyll b and total chlorophyll contents increased at the beginning of drought treatment, and then decreased with increasing drought stress. The chlorophyll content of f. viridis W. D. Xu f. nov Picea mongolica decreased with drought stress. The ratio of chlorophyll a/b decreased from maximum to minimum in f. viridis W. D. Xu f. nov Picea mongolica, but decreased in a relative small extent in f. purpurea W. D. Xu f. nov. It's proved that f. purpurea W. D. Xu f. nov Picea mongolica had a larger drought-resistance capacity than f. viridis W. D. Xu f. nov, and f. rubra W. D. Xu f. nov was a typical transitional ecotype from f. purpurea W. D. Xu f. nov to f. viridis W. D. Xu f. nov.

[Photosynthetic characteristics of three tree species seedlings in Changbai Mountain under different CO2 concentrations].

The photosynthetic characteristics of three-year-old seedlings of coniferous Pinus koraiensis and Pinus sylvestriformis and broadleaf Fraxinus mandshurica in open-top chambers in Changbai Mountain were studied. Seedlings were planted at four different conditions respectively:elevated CO2 concentration(700 and 500 mumol.mol-1) and ambient CO2 concentration (control chamber and in open field). After treating of two growing seasons in the first two years, seedlings were continuously grown under different CO2 concentration for another eight weeks. The results indicated that the photosynthetic capacity of three species was enhanced under high CO2 concentration in the first two growing seasons. The maximum net photosynthetic rates and light response parameters of different tree species were different at the same CO2 concentration. No photosynthetic acclimation was observed in the third growing season except Pinus sylvestriformis seedlings grown under 500 mumol.mol-1 CO2. The increase or decrease of net photosynthetic rates and light response parameters were related to the time of CO2 treatment. Elevated CO2 concentration could alter the ability of utilizing strong light and low light of seedlings.