Membrane processes fermentation broths

The incomplete comprehension of mass transfer mechanisms in ED membrane systems is in all probability responsible for the difficult design of industrial plants and for their limited diffusion. For instance, in the food biotechnology sector ED applications are still in their infancy since quite a limited number of the novel processes studied so far in laboratory- and pilot-scales and reviewed here have been converted into industrial realities yet, except for the recovery of the sodium salt of unspecified organic acid from clarified fermentation broths, as well as amino and organic acids (Gillery et al., 2002). 

Fermentation is typically conducted in dilute suspension culture. The low concentration in such systems limits reaction efficiency, and the presence of particulate and colloidal solids poses problems for product recovery and purification. By circulating the fermentation broth through an ultrafiltration system, it is possible to recover product continuously as they are generated while minimizing loss of enzyme or cells and keeping product concentration in the bioreactor below the self-inhibition level for the biocatalyst. This process is referred to as perfusion. As the ultrafiltration unit is part of the production process, the entire system is often considered a membrane reactor. 

Solvent extraction of penicillin from fermentation broths has been well documented in the literature. Penicillin G and penicillin V can be efficiently extracted with amyl acetate or butyl acetate at pH 2.5-3.0 and at 0° to 3°C.33 Schiigerl1 systematically reviewed solvent extraction of different forms of penicillin from fermentation broths. Figure 1 shows an integrated process for the extraction of penicillin G from clarified broth of Penicillium chryso-genurn fermentation.1 Penicillin G is converted to 6-amino penicillanic acid and phenylacetic acid at pH 8 in a 10 L Kiihni extractor by penicillin G-amidase immobilized in an emulsion liquid membrane. The 6-amino penicillanic acid is subsequently converted to ampicillin at pH 6 and the enzyme is recycled. 

Due to their greater chemical and thermal stabilities and narrower pore size distributions compared to polymer membranes, ceramic membranes are attractive in a number of filtration applications related to the fermentation broths. They can be used for either upstream or downsueam processing. 

Cheryan, M., 1994, Processing ethanol fermentation broths and stillage with ceramic membranes, presented at 3rd Int Conf. Inorg. Membr., Worcester, MA, USA. 

An example of this configuration is filtration of the methane fermentation broth from a sewage sludge liquor [Kayawake et al., 1991]. The liquor is u eated anaerobically in a fermentor. The broth is pumped to a ceramic membrane module which is contained in the fermentor. The retentate is returned to the fermentor while the permeate is discharged to the environment This is schematically shown in Figure 8.2. Although the membrane module is enclosed in the bioreactor for compactness and process simplification, the membrane step in essence follows the fermentation step. 

Recovery from fermentation broth and separation of carboxylic acids, amino acids were tested by many authors using layered BLM, rotating, creeping, spiral-type FLM, HELM, HLM, and MHS-PV techniques of the OHLM processes. The research works for the last 15 years in this field classified according to the OHLM techniques with types of membrane walls and carriers used are provided in Table 13.7. 

Gryta [150] conducted integration of fermentation process with membrane distillation for the production of ethanol. The removal of by products, which tends to inhibit the yeast productivity, from the fermenting broth by MD process increased the efficiency and productivity of the membrane bioreactor. The ethanol concentration in permeate was 2-6 times higher than that in the fermenting broth. The enrichment coefficient was found to increase with decrease of ethanol concentration in the broth. 

In other words, how to link in a reliable way, with limited information, the macroscale process performance to local phenomena at the meso- (membrane pore) if not at the nano- (solute-solute or solute-barrier interactions) scale levels. To answer these questions, there is a need for a new methodology, based on chemical engineering principles, with a holistic approach involving well-balanced experimental/simulation/modeling parts. A first attempt to tackle this question was carried out a few years ago with a particular example the purification by ultrafiltration (UF) of a small neutral molecule from a fermentation broth, constituted of unknown peptides and proteins with sizes ranging on a very large scale [28-30]. 

Immiscible-liquid solvent extraction is a well-established practice for recovery, concentration, and purification of organophilic solutes (e.g., antibiotics, amino acids, vitamins) present in aqueous process streams such as fermentation broths or plant or animal tissue extracts [88]. The process is, however, frequently rendered difficult or impossible by problems of emulsification, loss of entrained solvent, and contamination by particulate impurities in the feed. Integrated membrane separation with liquid/liquid extraction is iUustrated in Fig. 9.7. 

Fermentation broths tend to be very dilute and contain complex mixtures of inorganic or organic substances. The recovery of a soluble product (MW range 500-2500 dalton) such as an antibiotic, organic acid or animal vaccine from fermentation broth takes several processing steps. The first step is the clarification of broth to separate the low molecular weight soluble product from microorganisms and other particulate matter such as cells, cell debris, husks, colloids and macromolecules from the broth me-dium.l l In this step, microporous membrane filters (MWCO 10,000 to... 

Today many industrial fermentation broth clarifications are performed using cross-flow MF/UF membrane modules.The advantage of CFF over traditional separation processes is not only in superior product flow rates but also in higher yields or lower product losses. Using diafiltration, up to 99% recovery can be obtained.f lt ... 

Electrodialysis uses stacks of pairs of anion- and cation-exchange membranes in deionizing water and in recovery of formic, acetic, lactic, gluconic, citric, succinic, and glutamic acids from their sodium and potassium salts in fermentation broths.114 This may have an advantage over processes that involve purification through calcium salts. Electrodialytic bipolar membranes have been used to recover concentrated mineral acids from dilute solution.115 They can be used to convert sodium chloride to hydrogen chloride and sodium hydroxide in a process that avoids the use of chlorine.116 Soy protein has been precipitated by... 

Membrane Processes in the Separation, Purification, and Concentration of Bioactive Compounds from Fermentation Broths... 

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