Effects of ultra-high-pressure treatment on the structural and functional properties of buckwheat 13S globulin

Components with strong adsorption capacity for cholates from buckwheat proteins were screened, separated and purified by several methods, and the effects of ultra-high-pressure(UHP) on the structure and function of buckwheat 13S globulin(BW13SG) were studied. Samples were treated by UHP at different p H(3.0 and 7.0) value(s) and at 100–500 MPa for 10–30 min. The results showed that the tertiary structure of BW13SG was partially denatured and aggregated. The decrease in the unordered structure indicated that UHP resulted in a looser secondary structure of BW13SG. UHP treatment also increased solubility, emulsion activity and stability, foaming capacity and stability. The samples treated at 500 MPa, p H 3.0 for 30 min had the most enhanced functionality. Moreover, under this condition, the sodium cholate and sodium deoxycholate adsorption capacities of BW13SG were both higher than 98% and the adsorption capacity of sodium taurocholate, which can be difficult to adsorb, was higher than 60%.

Optimization of Formulation and Processing Process of Milk Drink Supplemented with Whole Oat Kernels

The objective of this study was to study the stability of oat kernel-supplemented milk from two perspectives of formulation and processing process,with centrifugal precipitation rate,viscosity and sensory score as evaluation indices.After optimization,the results show that the optimal compound stabilizer formula was obtained as follows:0.04%gellan gum,0.020%carrageenan,0.020%sodium carboxymethyl cellulose and 0.20%microcrystalline cellulose.With single-factor experiments and orthogonal array design,the optimal processing process that provided the best stability as well as good taste was determined as follows:batching temperature 50℃,hydration time 40 min,homogenization pressure 30 MPa and filling temperature 15℃.

Metabolic engineering of Escherichia coli for the production of Lacto-N-neotetraose(LNnT)

Lacto-N-neotetraose(LNnT),one of the most important human milk oligosaccharides,can be used as infants’food addi-tives.Nowadays,extraction,chemical and biological synthesis were utilized to obtain LNnT,while these methods still face some problems such as low yield and high cost.The aim of current work is to construct a de novo biosynthesis pathway of LNnT in E.coli K12 MG1655.The lgtA and lgtB were first expressed by a plasmid,resulting in a LNnT titer of 0.04 g/L.To improve the yield of LNnT on substrate lactose,lacZ and lacI were knocked out,and lacY was over-expressed.As a result,the yield of LNnT on lactose increased from 0.01 to 0.09 mol/mol,and the titer of LNnT elevated to 0.41 g/L.In addition,the pathway was regulated using the titer of Lacto-N-triose II(LNTII)as a measure,and obtained a high titer strain of LNnT for 1.04 g/L.Finally,the gene expressions were fine-tuned,the titer of LNnT reached 1.2 g/L,which was 93%higher than the control strain,and the yield on lactose reached 0.28 mol/mol.The engineering strategy of pathway construction and modulation used in this study is applicable to facilitate the microbial production of other metabolites in E.coli.

Cloning,purification,and characterization of branched-chain α-keto acid decarboxylases from Lactococcus lactis strains with different 3-methylbutanal production abilities

Lactococcus lactis is an important food-grade microorganism that has been successfully applied as a starter to increase the level of 3-methylbutanal produced during the ripening of cheese.Three variants of branched-chain α-keto acid decarboxylase (KADC) were discovered in L.lactis strains with different 3-methylbutanal production abilities.Three genes encoding KADCs of varying lengths (KADC-long,KADC-middle,and KADC-short) were cloned and heterologously expressed into Escherichia coli.KADC activity was only detected in the E.coli cloned with the KADC-long-encoding gene.Homology modeling of the three KADC recombination proteins showed that an active-site residue (Glu462) and an S-pocket structure were necessary for the ability to catalyze substrates.KADC-long showed maximum activity at pH 7.0 and 30 ℃.The substrate hydrolysis and kinetic parameters demonstrated that KADC-long efficiently produces 2-methylbutanal and 3-methylbutanal.The heterologous expression of the full-length kdcA in low-3-methylbutanal-yield L.lactis strains increased their production yields.The results of this study demonstrate the function of the complete KADC in 3-methylbutanal production.

Storage stability of freeze-dried colostral whey powders with different additives

Effects of different additives(sucrose and maltodextrin)on storage stability of colostral whey(CW)powders packaged in aluminium-laminated polyethylene pouches were investigated under different storage conditions(4℃and 40%-70%relative humidity(RH),25℃and 50%RH,and 50℃and 20%-60%RH).All the samples stored under 50℃and 20%-60%RH showed the highest levels of lipid oxidation,Maillard reaction,proteolysis,and color difference,and the lowest immunoglobulin G(IgG)retention.Moisture contents showed an increase trend with increasing RH.Addition of sucrose into CW powders increased water adsorption capacity and Maillard reaction,whereas addition of maltodextrin showed the opposite effects.Maltodextrin as drying aids was suitable for keeping quality during storage.Sucrose did not clearly play any roles in protecting denaturation of IgG during 90-day storage.The low storage temperature and RH were helpful for keeping storage stability of CW powders with different additives.