Dear Colleagues,

Membrane technology is an important unit operation in the food and biotechnology industries. The most well-known and mature food applications are dairy (milk and whey), fruit juice (apple, pear, grape, citrus), fermented products (wine, beer, vinegar), animal products (gelatin, eggs), plant proteins (soy), and sugars (dextrose, sucrose, dextrins, high-fructose syrup). Ultrafiltration (UF) is the dominant technology in most food and dairy applications, e.g., for treating cheese whey, for concentrating milk proteins and clarification of fruit juices and sugar streams.

The industry that has especially benefited by membranes is biotechnology (pharmaceuticals, enzymes, fermentation). In addition, there is a growing nutraceutical industry that uses individual components in plants, milk and whey with specific biological activities to give health-promoting benefits and to treat certain physiological disorders. The separation of bioactive compounds from crude fermentation broths or plant extracts requires unit operations that are quite different from traditional chemical separation processes. It is important to maintain the compound's bioactivity while maximizing its purity and yield. However, these three parameters are often mutually exclusive. One problem is that the compound is at a low concentration of a few hundred ppm to 10% of the broth. Another is that the impurities could have physicochemical properties that are similar to the target compound of interest, making conventional separations difficult. The use of organic solvents for extraction and purification of nutraceuticals is increasing, which creates its own set of challenges. Many of the membranes used today were designed for aqueous systems and not for use with organic solvents.

If R&D activity is an indication of potential commercial application, the biggest users of membranes this past decade were agro-based industries, such as vegetable oil processors, producers of dextrose and hydrolyzed starch from corn and wheat, sugar (beet and cane) processors and manufacturers of biobased products such as ethanol, citric acid, lactic acid, acetic acid, methyl esters, etc. In the vegetable oil industry, degumming and nitrogen production for packaging by gas separation are now established and others are under development, such as solvent recovery by RO or nanofiltration (NF), deacidification by NF, dewaxing by MF and recovery of hydrogenation catalyst by MF. With organic acids produced by fermentation, several membrane technologies can be used in the same process scheme simultaneously, e.g., electrodialysis to purify the organic acid, NF to recycle and/or desalt the sugars and MF to separate microbial cells. Membranes can also be integrated into the reaction scheme to create "continuous membrane bioreactors" which can significantly improve productivity of enzyme hydrolysis and fermentations, as well as enhance treatment of wastewater.

We are seeking papers for this special issue of Membranes that reflect recent advances in the application of membranes in these industries.  Our goal is rapid publication of high-quality papers that will advance the science and facilitate successful commercialization of the technology.

Munir Cheryan
Guest Editor

• animal products
• alcoholic beverages (e.g., beer, wine)
• biotechnology
• biofuels (e.g., ethanol, biodiesel)
• bioproducts
• cheese manufacture
• corn (maize)
• dairy
• dextrose (glucose)
• egg
• fermentation
• fish processing
• food products
• fruit juices
• gelatin
• microorganisms
• oily wastewaters
• plant proteins
• potato processing
• soybean
• starch processing
• stillage (vinasse)
• sugar, beet and cane
• vegetable oil
• whey (WPC, WPI)