Nanofiltration food industry

While reverse osmosis and ultrafiltration were being established in several applications, there was a lack of available membranes with cutoffs between 400 and 4000 g/mol. Increasing interest in NF membranes developed in the last decade. An extensive review on principles and applications of nanofiltration has been published recently [38]. Nanofiltration is important for water softening [39] and removal of organic contaminants. In the food industry, nanofiltration can be applied for concentration and demineralization of whey, concentration of sugar and juice. Nanofiltration also finds application in the pulp and paper industry, in the concentration of textile dye effluents and in landfill leachate treatment. The improvement of solvent stabihty of available NF membranes opens a wide range of potential applications in the chemical and pharmaceutical industry as weU as in metal and acid recovery. 

The production of substances that preserve the food from contamination or from oxidation is another important field of membrane bioreactor. For example, the production of high amounts of propionic acid, commonly used as antifungal substance, was carried out by a continuous stirred-tank reactor associated with ultrafiltration cell recycle and a nanofiltration membrane [51] or the production of gluconic acid by the use of glucose oxidase in a bioreactor using P E S membranes [52]. Lactic acid is widely used as an acidulant, flavor additive, and preservative in the food, pharmaceutical, leather, and textile industries. As an intermediate product in mammalian metabolism, L( +) lactic acid is more important in the food industry than the D(—) isomer. The performance of an improved fermentation system, that is, a membrane cell-recycle bioreactors MCRB was studied [53, 54], the maximum productivity of 31.5 g/Lh was recorded, 10 times greater than the counterpart of the batch-fed fermentation [54]. 

Membrane technology is a mature industry and has been successfully applied in various food industries for separation of undesirable fractions from the valuable components of the feed streams. The industrial membranes are classified into various categories such as microfiltration, ultrafiltration, nanofiltration, reverse osmosis, and pervaporation. 

Currently, the pressure-driven membrane processes, reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF), are widely used in water treatment, biotechnology, food industry, medicine, and other fields (Baker 2004). However, one of the main problems arising from the operation of the manbrane units is membrane fouling, which seriously hampers the applications of manbrane technologies (Scot and Hughes 1996). 

Generally, a distinction can be made between membrane bioreactors based on cells performing a desired conversion and processes based on enzymes. In ceU-based processes, bacteria, plant and mammalian cells are used for the production of (fine) chemicals, pharmaceuticals and food additives or for the treatment of waste streams. Enzyme-based membrane bioreactors are typically used for the degradation of natural polymeric materials Hke starch, cellulose or proteins or for the resolution of optically active components in the pharmaceutical, agrochemical, food and chemical industry [50, 51]. In general, only ultrafiltration (UF) or microfiltration (MF)-based processes have been reported and little is known on the application of reverse osmosis (RO) or nanofiltration (NF) in membrane bioreactors. Additionally, membrane contactor systems have been developed, based on micro-porous polyolefin or teflon membranes [52-55]. 

Concerns about groundwater contamination and municipal water supply quality have driven much of the growth of various water treatment schemes involving nanofiltration as a stand-alone process or in combination with RO and/or UF in a broad range of water treatment systems delivering precise purity levels and attractive process economics. Other established applications include corn syrup concentration, recycling of water-soluble polymers, effluent treatment for the food and beverage industry, metal... 

The concept of coupling reaction with membrane separation has been applied to biological processes since the seventies. Membrane bioreactors (MBR) have been extensively studied, and today many are in industrial use worldwide. MBR development was a natural outcome of the extensive utilization membranes had found in the food and pharmaceutical industries. The dairy industry, in particular, has been a pioneer in the use of microfiltra-tion (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membranes. Applications include the processing of various natural fluids (milk, blood, fruit juices, etc.), the concentration of proteins from milk, and the separation of whey fractions, including lactose, proteins, minerals, and fats. These processes are typically performed at low temperature and pressure conditions making use of commercial membranes. 

RO membrane separation has been traditionally used for seawater and brackish water desalination, and production of high-purity water for food, pharmaceutical processing and industrial waste treatment, as discussed in Chapter 1. The development of nanofiltration (NF) membranes has opened up many areas of apphcation including water softening, removal of disinfection by-product precurson (trihalomethanes), removal of total organic carbon (TOC), food processing and industrial water treatment [5]. 

The reverse osmosis business that Sidney Loeb pioneered is now worth many billion euros annually. Installed reverse osmosis processes produce in excess of 13.5 billion cubic metres of drinking water annually and are now the leading desalination technology on a world basis. Additionally, more than 17,000 small industrial, ship-mounted and household reverse osmosis systems are also in use. Furthermore, the closely related processes of nanofiltration and ultrafiltration are very widely used throughout the manufacmring industries, including pharmaceuticals and food production. Such membrane processes also have important medical applications. 

The range of industrial applications to liquid filtration is very broad. Water purification is one of the most important applications in liquid filtration. The processes of water purification include microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO), depending on the size of the undesired particles/molecules to be removed. Some examples of industrial applications including fuel filters, water filters, carbon filter, and wet/dry filters are being widely used in the production of textile, cosmetics, food and beverage, electronic components, papers, ship builders, and oil and gas wells. 

This book was planned to commemorate the announcement of the first cellulose acetate membrane for reverse osmosis by Loeb and Sourirajan in 1960, which triggered R D activities for seawater desalination by membrane and eventually resulted in emergence of a novel industrial separation process. Membrane separation technologies that include reverse osmosis, nanofiltration, ultrafiltarion, membrane gas and vapor separation, pervaporation, membrane extraction, membrane distillation, bipolar membrane and others, touch nowadays all aspects of human life since they are applied in various branches of industries such as chemical process, petrochemical and petroleum, pharmaceutical, environmental and food processing industries. 

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