Series Of Ultrafiltration Membranes Research Articles

Impact of Processing Condition on Nutraceutical Potency of Soy Whey Hydrolysate

The present investigation aims to study the nutraceutical potency of soy whey hydrolysate, which can be incorporated as an antioxidant supplement in food products. The hydrolysate was passed through a series of ultrafiltration membranes (30 and 10 kDa MWCO) out of which only 10 kDa permeate showed 1.2-fold increased activity having stability range of pH 2–9. Under extreme pH, radical-scavenging activity decreased, retaining nearly 79% of the total original activity. More than 50% of antioxidant activity loss was observed at salt concentration >1.5 mM. Micronutrients such as Cu2+, Mn2+, Ca2+, Mg2+ and Co2+ in the reaction medium also reduced the ABTS scavenging activity up to >60%. Addition of phenolics and vitamins in hydrolysates showed strong synergistic effects with peptides. Gastrointestinal digestion resulted in 1.15-fold increase in the activity with pancreatic digestion. Such results prove the candidature of soy whey hydrolysate as potential ingredient to formulate functional foods. Practical Applications Antioxidant peptide-rich soy whey hydrolysate can be used as nutritional and antioxidant supplement in food formulation as they are rich in eight essential amino acids and bear a wide range of antioxidant stability during processing.

Characteristics of C-, N-DBPs formation from algal organic matter: Role of molecular weight fractions and impacts of pre-ozonation

Extracellular organic matter (EOM) and intracellular organic matter (IOM) of Microcystis aeruginosa have been reported to contribute to the formation of carbonaceous disinfection by-products (C-DBPs) and nitrogenous disinfection by-products (N-DBPs). Little is known about DBPs formation from different molecular weight (MW) fractions, especially for N-nitrosodimethylamine (NDMA). This study fractionated EOM and IOM into several MW fractions using a series of ultrafiltration membranes and is the first to report on the C-DBPs and N-DBPs formation from chlorination and chloramination of different MW fractions. Results showed that EOM and IOM were mainly distributed in low-MW (<1 KDa) and high-MW (>100 KDa) fractions. Additionally, the low-MW and high-MW fractions of EOM and IOM generally took an important part in forming C-DBPs and N-DBPs, either in chlorination or in chloramination. Furthermore, the effects of pre-ozonation on the formation of DBPs in subsequent chlorination and chloramination were also investigated. It was found that ozone shifted the high-MW fractions of EOM and IOM into lower MW fractions and increased the C-DBPs and N-DBPs yields to different degrees. As low-MW fractions are more difficult to remove than high-MW fractions by conventional treatment processes, therefore, activated carbon adsorption, nanofiltration (NF) and biological treatment processes can be ideal to remove the low-MW fractions and minimize the formation potential of C-DBPs and N-DBPs. Moreover, the use of ozone should be carefully considered in the treatment of algal-rich water.

Purification and characterization of novel antioxidant peptides of different molecular weights from mackerel Pneumatophorus japonicus protein hydrolysate

Mackerel (Pneumatophorus japonicus) proteins were hydrolyzed by five proteases: trypsin, papain, neutrase, acid protease, and flavourzyme. The hydrolysate treated by neutrase exhibited the highest antioxidant activity. Response surface methodology (RSM) was employed to optimize the hydrolysis conditions in an effort to obtain a mackerel protein hydrolysate (MPH) with the highest DPPH radical scavenging activity. The MPH was fractioned using a series of ultrafiltration membranes and five fractions, namely, MPH-I (>10 kDa), MPH-II (10-2.5 kDa), MPH-III (1-2.5 kDa), MPH-IV (0.4-1 kDa), and MPH-V (below 0.4 kDa), were obtained. DPPH radical scavenging activity, reducing power, hydroxyl radical scavenging activity, and the lipid peroxidation inhibition capability of these fractions were evaluated. The fractions in molecular weights <2.5 kDa (MPH-III, MPH-IV, and MPH-V), which occupied 93.4% of the total fractions, showed the strongest antioxidant activity; and the antioxidant activities of the three fractions are similar to each other. Using SP Sephadex C-25 and Sephadex G-25 columns, eight fractions were obtained from the MPH (<2.5 kDa). The isolated peptide I (1 664 kDa) displayed the highest DPPH radical scavenging activity. Therefore, MPH is a potential source of antioxidant peptides.

Factors controlling N-nitrosodimethylamine (NDMA) formation from dissolved organic matter

The formation of cancinogenic nitrosamines, esp. N-nitrosodimethylamine (NDMA) in water and wastewater treatment plants has drawn much attention in recent years. Dissolved organic matter from the transported Luan River water as water source of Tianjin was fractionated with different XAD resins and a series of ultra-filtration membranes with molecular weight (MW) cut-offs of 5k Da, 3k Da, and 1k Da, respectively. The NDMA yields from the raw water and each fraction were measured to investigate their role in NDMAyield. Results indicated that the hydrophilic fraction had a higher NDMA yield than those of hydrophobic fraction and transphilic fraction. The fraction with MW below 1k Da had a higher NDMAyield than that with larger MW. NDMA formation increased as the dissolved organic carbon (DOC) to dissolved organic nitrogen (DON) ratio decreased, which indicated that DON might serve as the real important precursor for NDMA. The correlation between NDMA yield and specific ultraviolet absorbance at 254 nm (SUVA254) suggested that the latter might not represent the specific precursors for NDMA in the water. Besides the water quality, the influences of pH, disinfectant dosage, and disinfection contact time on the formation of NDMA were also examined. These results will help water treatment plants establish measures to control this harmful disinfection by-product.

Measurement of dissolved organic nitrogen in a drinking water treatment plant: Size fraction, fate, and relation to water quality parameters

This paper investigates the characteristics of dissolved organic nitrogen (DON) in raw water from the Huangpu River and also in water undergoing treatment in the full-scale Yangshupu drinking water treatment plant (YDWTP) in Shanghai, China. The average DON concentration of the raw water was 0.34 mg/L, which comprised a relatively small portion (~ 5%) of the mass of total dissolved nitrogen (TDN). The molecular weight (MW) distribution of dissolved organic matter (DOM) was divided into five groups: > 30, 10–30, 3–10, 1–3 and < 1 kDa using a series of ultrafiltration membranes. Dissolved organic carbon (DOC), UV absorbance at wavelength of 254 nm (UV254) and DON of each MW fraction were analyzed. DON showed a similar fraction distribution as DOC and UV254. The < 1 kDa fraction dominated the composition of DON, DOC and UV254 as well as the major N-nitrosodimethylamine formation potential (NDMAFP) in the raw water. However, this DON fraction cannot be effectively removed in the treatment line at the YDWTP including pre-ozonation, clarification and sand filtration processes. The results from linear regression analysis showed that DON is moderately correlated to DOC, UV254 and trihalomethane formation potential (FP), and strongly correlated to haloacetic acids FP and NDMAFP. Therefore, DON could serve as a surrogate parameter to evaluate the reactivity of DOM and disinfection by-products FP.

Preparation and antioxidant activity of enzymatic hydrolysates from purple sea urchin ( Strongylocentrotus nudus) gonad

Purple sea urchin ( Strongylocentrotus nudus) gonad was treated separately with neutral protease, papain, pepsin and trypsin. The resultant hydrolysates were fractionated using a series of ultrafiltration membranes (molecular weight cut-offs of 10, 5, 3 and 1 kDa). Five fractions were prepared from each hydrolysate and the corresponding molecular weight ranges were below 10 kDa, 5–10 kDa, 3–5 kDa, 1–3 kDa and below 1 kDa. The peptide fractions were evaluated for antioxidant activity by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and reducing power assay. Results indicated that all peptide fractions possessed DPPH radical scavenging capacity and reducing power in a dose-dependent manner. For all four hydrolysates, the below 1 kDa fractions exhibited the highest DPPH radical scavenging capacity. The below 1 kDa fractions prepared with neutral protease, papain and pepsin, and the 1–3 kDa fraction prepared with trypsin showed the highest reducing capacity among corresponding hydrolysates.

Preparation and in vitro antioxidant activity of enzymatic hydrolysates from oyster (Crassostrea talienwhannensis) meat

SummaryOyster is an abundant resource from ocean, which contains high content of protein. In the present study, oyster (Crassostrea talienwhannensis) meat was digested with three proteases including papain, neutrase and alcalase respectively and the derived hydrolysates were fractionated using a series of ultrafiltration membranes (molecular weight cut‐offs of 10, 5, 3 and 1 kDa). The resultant peptide fractions were evaluated for antioxidant activity using 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) assay and reducing power assay. Results indicated that oyster meat hydrolysates (OMHs) possessed DPPH radical scavenging capacity and reducing power in a dose‐dependent manner. The fractions below 1 kDa showed the strongest overall antioxidant activity. The present study demonstrated that the antioxidant potent of OMHs was strongly related to their concentration, size and amino acid composition.

Purification and characterization of antioxidative peptides from protein hydrolysate of lecithin‐free egg yolk

AbstractThe protein extracted from lecithin‐free egg yolk, normally discarded by lecithin processing plants, was hydrolyzed with the aid of Alcalase, a commercial enzyme. The hydrolysate was separated through a series of ultrafiltration membranes with molecular weight cutoffs of 10, 5, and 1 kDa; and three types of permeates including 10 K (permeate from 10 kDa), 5 K (permeate from 5 kDa), and 1 K (permeate from 1 kDa) were obtained. The antioxidative efficacy of hydrolysates so obtained was investigated and compared with α‐tocopherol. Furthermore, two different peptides showing strong antioxidative activity were isolated from the hydrolysates by using consecutive chromatographic methods including ion exchange chromatography on a SP‐Sephadex C‐25 column, gel filtration on a Sephadex G‐25 column, and high‐performance liquid chromatography on an octadecylsilane column. The purity of the peptides was identified using capillary electrophoresis. The isolated peptides were composed of 10 and 15 amino acid residues, and both contained a leucine residue at their N‐terminal positions.

Induction of collagenase production in Vibrio B-30

The inducible nature of an extracellular collagenase produced by a marine Vibrio (Vibrio B-30, ATCC 21250) was demonstrated by observing the increase in extracellular collagenase activity after the addition of collagen to cell cultures in the latter part of the exponential growth phase. When collagenase-hydrolyzed collagen was added, the lag time required before collagenase production was detected decreased significantly compared with cultures receiving collagen. Cells preinduced to synthesize collagenase did not produce the enzyme when collagen was removed from the culture medium. Incorporation of penicillin G had no effect on final collagenase activity levels in suspensions of Vibrio B-30 in complete medium supplemented with collagen. However, chloramphenicol and tetracycline inhibited collagenase production, indicating that de novo protein synthesis was necessary for the appearance of activity. Attempts to isolate the inducing substance(s) involved filtering hydrolyzed collagen through a series of ultrafiltration membranes. The lowest-molecular-weight fraction of collagen hydrolysate with inducing ability was between 1,000 and 10,000. Gel filtration of this fraction on Sephadex G-50 resulted in the appearance of three protein peaks, two of which were capable of inducing collagenase production. Results from amino acid composition and N-terminal amino acid analysis suggest that the inducing substance originates from the polar helical portion of the collagen molecule.