Recovery and purification of potato proteins from potato starch wastewater by hollow fiber separation membrane integrated process

Potato starch wastewater contains high-concentration potato proteins which have great potential in the fields of food and health care. Most researches on potato protein recovery by membrane separation technique are focused on flat sheet or tubular ultrafiltration (UF) and reverse osmosis (RO) membranes and lack the further protein purification and the in-depth discussions on the fouling behavior. In this laboratory-scale study, potato proteins were recovered and purified from the simulated potato starch wastewater by the self-made hollow fiber (HF) UF and nanofiltration (NF) separation membrane integrated process. 85.62% potato proteins with high molecular weight in the potato starch wastewater could be retained by UF membrane and 92.1% potato proteins with low molecular weight were rejected by NF membrane. The concentrated solution after UF and NF filtration was desalinated and purified by diluting the solution eight times and filtering the diluted solution with UF membrane. Both types of HF membranes, UF and NF, suffered the inevitable membrane fouling. After the traditional physical washing and chemical cleaning, water flux of UF and NF membranes can be effectively recovered. The corresponding recovery rates of UF and NF membranes can reach 93.5% and 84.7%, respectively. The hollow fiber UF-NF separation membrane integrated process was proved to be a promising technique of high-purity potato protein recovery from potato starch wastewater.     

PROCESSING WHEY-TYPE BY-PRODUCT LIQUIDS FROM COTTONSEED PROTEIN ISOLATION WITH ULTRAFILTRATION AND REVERSE OSMOSIS MEMBRANES

Cottonseed wheys resulting from protein isolation from cottonseed flour were processed by semi-permeable ultrafiltration (UF) and reverse osmosis (RO) membranes. The UF membrane fractionated the soluble whey constituents by retaining protein and passing through salts, carbohydrates and other non-protein components along with most of the water. The UF membrane effluent was then processed through an RO membrane to recover a secondary product containing the whey materials not retained in the protein product from the UF membrane. The feasibility of recycling effluent from the RO membrane for reuse in subsequent protein extractions was demonstrated. Thus, the threat of water pollution from effluent disposal could be eliminated completely and process water requirements drastically reduced. Spray-dried UF protein concentrates were tested for utilization in protein fortification of breads and noncarbonated beverages and as whipping products. They exhibited commercial potential for use in these food applications. The economics of processing the whey-type liquids by the membrane process under investigation were analyzed. Membrane processing of wheys by each of two alternative whey processing systems proved to be economically attractive.     

Egg White Lysozyme Purification by Ultrafiltration and Affinity Chromatography

Isolation and purification of lysozyme from hen egg white was studied using a two-step procedure. The egg white was diluted 5- to 9-fold with sodium phosphate buffer, and then processed by sequential dilution diafiltration using a UF membrane (molecular weight cut-off 300,000 dalton). The membrane process increased the specific activity of lysozyme 6-fold, and recovered 96% of lysozyme activity. The permeate from diafiltration was further purified by affinity chromatography using chitin as adsorbent. The second step of the process yielded a product of specific activity of 70,400 units/mg protein. The overall lysozyme recovery was 79%.     

Hydrolysis of Soybean Proteins by a Vortex Flow Filtration Membrane Reactor with Aspergillus oryzae Proteases

Proteases consisting of various endo- and exo-proteases were prepared by homogenizing Aspergillus oryzae mycelia using a French-press. The hydrolysis of 1% soybean proteins was carried out at 35°C and pH 7.0. The back-pressure, flux and rotational speed of the reactor affected the hydrolysis rate and productivity. The reactor system could be operated in a continuous process by replenishing the substrate solution, with the concentration adjusted to maintain 0.43% substrate in the reaction vessel. Permeate flux gave a constant product as shown by molecular weight distribution and amino acid composition.     

Performance of enzymatic wheat gluten hydrolysis in batch and continuous processes using Flavourzyme

The aim of this study was to investigate the process performance of wheat gluten hydrolysis with Flavourzyme in the conventional batch and in an enzyme membrane reactor system. The release of amino acids and peptides from wheat gluten using Flavourzyme in a batch process (T 50 °C, pH 5) is limited due to product inhibition. Investigation of Flavourzyme inhibition kinetics by l-amino acids revealed that the strongest inhibition was observed by l-cysteine. Thus, application of an enzyme membrane reactor with continuous product removal and substrate and enzyme retention was assessed. The highest productivity in the enzyme membrane reactor system was found using a 10 kDa molecular weight cut-off polyethersulfone membrane. This resulted in an increased product enzyme ratio from 2.1 mg product/nkat in the conventional batch process to 4.9 mg product/nkat with the enzyme membrane reactor after 20 h. The enzyme membrane reactor retained 80% of the initial space-time yield (STY_init 5 g/L/h) after nine days.     

Purification of Steviosides by Membrane and Ion Exchange Processes

An ultrafiltration (UF) process removed more than 96% of the pigments and recovered 45% of steviosides non-nutritive sweetener from an extract of leaves. UF retentate was further processed by diafiltration (DF), and the permeate was concentrated by reverse osmosis (RO). The membrane processes (UF, DF, RO) achieved an overall steviosides recovery of more than 90% with product purity 46%. Final purification was conducted by two consecutive mixed bed ion exchange processes. The ion exchangers improved purity of the final product to 90%.     

Rennet coagulation of sheep milk processed by ultrafiltration at low concentration factors

The ultrafiltration (UF) of sheep milk is carried out in concentration mode in order to evaluate the variation of the rennet clotting properties of the concentrates as a function of the volumetric concentration factors up to a value of 2.0. The UF unit is equipped with 25.5 cm² of membrane surface area. The cellulose acetate laboratory – made membrane has a molecular weight cut-off of 7000 Da. The evolution pattern of the rennet clotting properties of the skimmed sheep milk feed and UF retentates was assessed by the Optigraph. A significant increase on curd firmness and rate of curd firming was detected with the increase of the protein concentration, while RCT show a tendency to increase with milk protein content. The variation of curd firmness and rate of curd firming with the protein concentration was linear and correlations were established.     

膜技术分离纯化金银花绿原酸提取液工艺研究

研究膜技术分离纯化绿原酸提取液的过程。以金银花为原料,以平均通量、膜截留率、绿原酸透过率为指标,比较3 种微滤膜MF1、MF2 和MF3,4 种超滤膜UF1、UF2、UF3 和UF4,及两种反渗透膜RO1 和RO2 对绿原酸提取液的过滤特性,并研究浓缩液的洗滤对绿原酸截留率的影响。结果表明：MF1、UF1 和RO2膜的过滤性能明显优于其他同类型膜,使用MF1-UF1-RO2 膜组合处理效果最佳,其绿原酸回收率可达67.75%,产品纯度可达13.21% 以上;同时,洗滤可进一步提高处理效果,经间歇洗滤后,MF1 膜的绿原酸截留率可由9.54% 降低到1.17%,UF2 膜的绿原酸截留率可由32.36% 降低到20.11%。     

The ultrafiltration molecular weight cut-off has a limited effect on the concentration and protein profile during preparation of human milk protein concentrates

Optimizing protein intake for very low birth weight (<1,500 g) infants is fundamental to prevent faltering postnatal growth with the potential association of impaired neurodevelopment. The protein content of human milk is not sufficient to support the growth of very low birth weight infants. To meet their elevated protein requirements, human milk is currently fortified using typically bovine milk-based protein isolates (>85% on a dry basis). However, these products have several limitations for use in this vulnerable population. To overcome the shortcomings of bovine milk-based protein supplement, a human milk protein concentrate (HMPC) was developed. In preliminary attempts using 10 kDa ultrafiltration (UF) membranes, it was not possible to reach the protein content of commercial protein isolates, presumably due to the retention of human milk oligosaccharides (HMO). Consequently, it was hypothesized that the use of a UF membrane with a higher molecular weight cut-off (50 kDa rather than 10 kDa) could improve the transmission of carbohydrates, including HMO, in the permeate, thus increasing the protein purity of the subsequent HMPC. The results showed that permeate fluxes during the concentration step were similar to either UF molecular weight cut-off, but the 50-kDa membrane had a higher permeate flux during the diafiltration sequence. However, it was not sufficient to increase the protein purity of the human milk retentate, as both membranes generated HMPC with similar protein contents of 48.8% (10 kDa) and 50% (50 kDa) on a dry basis. This result was related to the high retention of HMO, mainly during the concentration step, although the diafiltration step was efficient to decrease their content in the HMPC. As the major bioactive proteins (lactoferrin, lysozyme, bile salt stimulated lipase, and α1-antitrypsin) in human milk were detected in both HMPC, the 50-kDa membrane seems the most appropriate to the preparation of HMPC in terms of permeation flux values. However, improving the separation of HMO from proteins is essential to increase the protein purity of HMPC.     

膜集成工艺浓缩灵芝水提液的研究

高效节能的膜集成技术已开始应用于食品和药用植物中有效成分的分离提取。文中针对灵芝提取液的特性,依据微孔过滤(MF)、超滤(UF)、纳滤(NF)各种膜对特定物质的选择分离性能,设计了新型膜集成工艺,即筛网和滤纸粗过滤除杂和MF净化处理,进而用不同切割分子质量(MWCO)膜进行两级UF、最后用NF净化浓缩灵芝水提液的创新技术。在操作压力≤0.20 MPa和15 m/s的高膜面流速,1.0 mL/(cm~2·h)恒通量模式下,灵芝水提液先后经MWCO分别为5万的聚丙烯腈(PAN)膜和1万的醋酸纤维素(CA)膜进行UF批次处理。UF渗透液再经截留分子质量为1 50～300的DK(标准)型聚酰胺(PA)膜进行纳滤浓缩,浓缩倍数达6倍时,渗透通量在0.92～0.33 mL/(cm~2·h),纳滤渗透液的色度在浓缩过程稳定在70～80,有效成分截留率高。     

THE FOULING AND CLEANING OF ULTRAFILTRATION MEMBRANES DURING THE FILTRATION OF MODEL TEA COMPONENT SOLUTIONS

Proteins and polyphenols are the principal fouling constituents in the ultrafiltration (UF) of black tea liquor. The aim of this study was to determine the relative importance of individual components in the fouling process, to investigate any synergetic interactions that were occurring and to compare the cleaning characteristics of different fouled membranes. A 30‐kD molecular weight cutoff polysulfone UF membrane in dead‐end mode was challenged with model solutions of tea components. Model solutions consisted of tea proteins, theaflavins (TFs), thearubigins and caffeine. Sodium hydroxide was used as a cleaning reagent. Permeate flux decline curves were presented for single components and mixtures. Individual component transfer fluxes and rejections were also presented. An unexpected finding was that protein in a mixture with TFs could permeate the membrane to a degree, while a protein solution in the absence of the polyphenol was completely rejected. The inspection of membranes fouled by different solutions revealed different foulant morphologies. Membrane cleaning with 0.2 wt % sodium hydroxide was generally found to be effective.     

Production of okara and soy protein concentrates using membrane technology

Microfiltration (MF) membranes with pore sizes of 200 and 450 nm and ultrafiltration (UF) membranes with molecular weight cut off of 50, 100, and 500 kDa were assessed for their ability to eliminate nonprotein substances from okara protein extract in a laboratory cross-flow membrane system. Both MF and UF improved the protein content of okara extract to a similar extent from approximately 68% to approximately 81% owing to the presence of protein in the feed leading to the formation of dynamic layer controlling the performance rather than the actual pore size of membranes. Although normalized flux in MF-450 (117 LMH/MPa) was close to UF-500 (118 LMH/MPa), the latter was selected based on higher average flux (47 LMH) offering the advantage of reduced processing time. Membrane processing of soy extract improved the protein content from 62% to 85% much closer to the target value. However, the final protein content in okara (approximately 80%) did not reach the target value (90%) owing to the greater presence of soluble fibers that were retained by the membrane. Solubility curve of membrane okara protein concentrate (MOPC) showed lower solubility than soy protein concentrate and a commercial isolate in the entire pH range. However, water absorption and fat-binding capacities of MOPC were either superior or comparable while emulsifying properties were in accordance with its solubility. The results of this study showed that okara protein concentrate (80%) could be produced using membrane technology without loss of any true proteins, thus offering value addition to okara, hitherto underutilized. Practical Application: Okara, a byproduct obtained during processing soybean for soymilk, is either underutilized or unutilized in spite of the fact that its protein quality is as good as that of soy milk and tofu. Membrane-processed protein products have been shown to possess superior functional properties compared to conventionally produced protein products. However, the potential of membrane technology has not been exploited for the recovery of okara protein. Our study showed that protein content of okara extract could be improved from approximately 68% to approximately 81% without losing any true proteins in the process.     

Casein Hydrolysate Produced Using a Formed-in-Place Membrane Reactor

Casein hydrolysate was continuously produced by hydrolysis of bovine casein with Protease Type XXIII (from Aspergillus oryzue) in a pilotscale formed-in-place membrane reactor. A high percentage (>99%) of TCA soluble nitrogen in the hydrolysate (product) was achieved after 45 min at 37°C and pH 7. The product was completely soluble over pH range 2–9. Water sorption increased 4 to 6.5 times at water activity of 0.35–0.95 as compared to intact casein. The immunologically active casein and immunologically active whey protein in the product were reduced 99% and 97%, respectively. Long term operation showed that the membrane reactor maintained steady production of casein hydrolysate longer than 17 hr.     

超滤处理木薯淀粉酒精废液及净化液回用研究

研究用超滤膜处理预处理过的木薯淀粉酒精废液,以脱色率及COD去除率作为鉴定指标;并测定处理后净化液的回用效果.试验表明,废液先经过0.3 MC筛网和4000 r/min离心20 min的预处理,再经截流分子量为1万的超滤膜处理后,脱色率为27.7%,COD去除率为34.7%,且膜清洗容易.膜透过液回用效果明显好于未经膜处理的废液,10万膜和1万膜透过液的回用率均可达到80%.     

Impact of ultrafiltration and nanofiltration of an industrial fish protein hydrolysate on its bioactive properties

BACKGROUND: Numerous studies have demonstrated that in vitro controlled enzymatic hydrolysis of fish and shellfish proteins leads to bioactive peptides. Ultrafiltration (UF) and/or nanofiltration (NF) can be used to refine hydrolysates and also to fractionate them in order to obtain a peptide population enriched in selected sizes. This study was designed to highlight the impact of controlled UF and NF on the stability of biological activities of an industrial fish protein hydrolysate (FPH) and to understand whether fractionation could improve its content in bioactive peptides. RESULTS: The starting fish protein hydrolysate exhibited a balanced amino acid composition, a reproducible molecular weight (MW) profile, and a low sodium chloride content, allowing the study of its biological activity. Successive fractionation on UF and NF membranes allowed concentration of peptides of selected sizes, without, however, carrying out sharp separations, some MW classes being found in several fractions. Peptides containing Pro, Hyp, Asp and Glu were concentrated in the UF and NF retentates compared to the unfractionated hydrolysate and UF permeate, respectively. Gastrin/cholecystokinin‐like peptides were present in the starting FPH, UF and NF fractions, but fractionation did not increase their concentration. In contrast, quantification of calcitonin gene‐related peptide (CGRP)‐like peptides demonstrated an increase in CGRP‐like activities in the UF permeate, relative to the starting FPH. The starting hydrolysate also showed a potent antioxidant and radical scavenging activity, and a moderate angiotensin‐converting enzyme (ACE)‐1 inhibitory activity, which were not increased by UF and NF fractionation. CONCLUSION: Fractionation of an FPH using membrane separation, with a molecular weight cut‐off adapted to the peptide composition, may provide an effective means to concentrate CGRP‐like peptides and peptides enriched in selected amino acids. The peptide size distribution observed after UF and NF fractionation demonstrates that it is misleading to characterize the fractions obtained by membrane filtration according to the MW cut‐off of the membrane only, as is currently done in the literature. Copyright © 2010 Society of Chemical Industry     

Ultrafiltration for Recovery and Reuse of Peptidoglutaminase in Protein Deamidation

Ultrafiltration (UF) of B. circulans cell extract using a 100kd hollow-fiber membrane had no effect on peptidoglutaminase (PGase) activity and allowed 34 and 26% of PGases I and II to permeate. UF, with 30kd spiral membrane, slightly increased PGase activity in retentate but no activity was detected in permeate. Retentate was used to sequentially deamidate four batches of a soy protein hydrolysate at 30°C for 2 hr, then PGase was recovered by UF. The 100kd membrane resulted in substantial PGase loss in sequential tests due to permeation and inactivation. A 100% conversion and 97% of PGase were obtained after tests with the 30 kd membrane. Multiple recovery and use of PGase by a suitable membrane is possible.     

DFA III production from inulin with inulin fructotransferase in ultrafiltration membrane bioreactor

An ultrafiltration membrane bioreactor was used for the production of DFA III from enzymatic conversion of inulin. Compared with the traditional batch reactor, the productivity and purity of DFA III could be markedly enhanced and product inhibition was removed and IFTase could be continuously used for six runs in the UF membrane bioreactor. When the substrate concentration was 100 g/L, the concentration of DFA III was about 78.4 g/L, while the productivity and purity of DFA III could attain about 2385 and 92%, respectively.     

EFFECTS OF INTERMOLECULAR INTERACTIONS AND MOLECULAR ORIENTATION ON THE FLUX BEHAVIOR OF XANTHAN GUM SOLUTIONS DURING ULTRAFILTRATION

Conformational changes of xanthan gum as a function of concentration were investigated to elucidate its unusual flux behavior during ultrafiltration (UF). The contribution of hydrogen bonding on structure formation and the molecular orientation of xanthan gum on the flow characteristics were studied rheomechanically and rheo-optically. Known to affect xanthan structure at low concentrations, hydrogen bonding unexpectedly did not show significant influence on xanthan rheological properties up to 2 wt %. The ordered layers formed on the membrane surface proved responsible for the enhanced water removal during UF. This unique behavior could be attributed to the formation of aligned molecular orientation in addition to the viscosity increases during the biphasic region. Significant differences were observed between xanthan fermentation broth and solutions made of commercial xanthan, suggesting the need to control the salt concentration in fermentation broth in order to make UF an effective recovery process for xanthan gum after fermentation.

PRACTICAL APPLICATIONS

The knowledge gained from the present study strengthens fundamental understandings on the conformational changes of xanthan biopolymers during the recovery of xanthan gum from fermentation broth using ultrafiltration (UF). By taking advantage of the aligned molecular orientation, along with controlling the salt concentration in the fermentation broth, UF could be operated at elevated flux to speed up the removal of water from the viscous fermentation broth. The technology should find broad applications in the fermentation industry, especially where viscosity is of concern during the separation and purification of the product.     

Influence of flocculation and adsorption as pretreatment on the fouling of ultrafiltration and nanofiltration membranes: application with biologically treated sewage effluent

Membrane fouling is a critical limitation on the application of membranes to wastewater reuse. This work aims to understand the fouling phenomenon which occurs in ultrafiltration (UF; 17500 molecular weight cutoff (MWCO)) and nanofiltration (NF; 250 MWCO) membranes, with and without pretreatment. For this purpose, the molecular weight (MW) distribution of the organics has been used as a parameter to characterize the influent, the permeate, and the foulant on the membrane surface. The variation of foulant concentration on the membrane due to pretreatment of the influent by flocculation and/or adsorption was investigated in detail. With the UF membrane, the peak of the MW distribution of organics in the permeate depended on the pretreatment; for example, the weight-averaged MW (Mw) of 675 without pretreatment shifted down to 314 with pretreatment. In the case of the NF membrane, the Mw of organics in the permeate was 478 (without pretreatment) and 310 (with flocculation followed by adsorption). The Mw of the organics in the foulant on the membrane surface was 513 (UF) and 192 (NF) without pretreatment and 351 (UF) and 183 (NF) after pretreatment with flocculation followed by adsorption, respectively. Without the pretreatment, the foulant concentration was higher on both membranes. The difference was more significant on the UF membrane than on the NF membrane. For both membranes, the flocculation-and-then-adsorption pretreatment proved very effective.     

Efficiency of cleaning agents for an inorganic membrane after milk ultrafiltration.

Cleaning of inorganic membranes after ultrafiltration (UF) of skim milk has been assessed using hydraulic, physicochemical and spectroscopic (i.r. and X-ray photoelectron spectroscopy) measurements. A cleaning sequence using hypochlorite alone or hypochlorite followed by HNO3 restored the membrane hydraulic resistance, in contrast to cleaning with HNO3 alone. When using NaOH, addition of Ca complexants (EDTA, gluconate, tripolyphosphate) and surfactants was required to obtain similar results. Three types of criteria (hydraulic, kinetic, chemical) are available to assess the effect of the sequestrant and surfactant types. In all the cases studied, traces of protein and Ca were detected on and within the membrane after cleaning. Nevertheless, it was concluded that it is possible to develop a single-step alkaline product to clean inorganic milk UF membranes if suitable surfactants and Ca sequestrants are included in its formula.