Fermention processes process separate enzymatic

Simultaneous saccharification and fermentation (SSF) one-stage enzymatic hydrolysis, but the fermentation of pentoses and hexoses takes place in separate process steps. 

Simultaneous saccharification and co-fermentation (SSCF) one-stage enzymatic hydrolysis of cellulose and fermentation of pentoses and hexoses all in one process step. The upstream hydrolysis of the hemicellulose takes place in a separate process step. 

Malic acid (hydroxybutanedioic acid) is a chemical intermediate and is also used as a food flavor enhancer. It can be made by several routes. U.S. 5,210,295 (to Monsanto) describes a nonenzymatic process. U.S. 4,772,749 (to Degussa) describes recovery of malic acid from the product of enzymatic conversion of fumaric acid. U.S. 4,912,042 (to Eastman Kodak) describes an enzymatic separation process for separating the L- and D-isomers. U.S. 5,824,449 (to Ajinomoto Co.) describes a selective fermentation from maleic acid. Estimate the cost of production of D-malic acid by each process and determine which is cheapest. 

Direct product precipitation allows pure recovery without need of further separation steps. Contamination by organic solvents is thereby avoided, which is often a problem for drug and food applications. A fermentation process that removes lactic acid by in situ crystallization with calcium ions was one of the first successful applications of a whole cell ISPR process [11]. Recently, the potential of in situ precipitation was shown for the solid-solid enzymatic conversion of Ca-maleate to Ca-D-malate. In situ crystallization processes employing whole cells are expected to be increasingly applied in the recovery of carboxylic acids, antibiotics, and proteins. 

NF technology is used in the pharmaceutical and biotechnology industry to recover antibiotics from fermentation processes. A schematic flow diagram of NF separation for recovery of 6-APA is shown in Figure 3.25 [10]. 6-AminopeniciUanic add (6-APA, MW 216 Da) is an intermediate in the manufacture of synthetic peniciUin and can be manufactured by an enzymatic process. A medium-sized plant produces 15—20 tons of mother liquor per day. NF (solvent stable membrane is used) separates the 6-APA (in the reten-tate) from the other Hquor at 60—80 kg/d and is recycled to the extraction unit, thereby minimising product losses (recovery is 90—95%). 

This is a two-step process in which the hydrolysis of the pretreated biomass is followed by the fermentation process, both taking place separately. The hydrolysis process uses acid or an enzymatic treatment, which converts the cellulose and hemicellulose to fermentable sugars. In the fermentation stage, the sugars are transformed to yield ethanol by the action of microorganisms. 

The fifth paper, "A Separative Bioreactor Direct Product Capture and pH Control," presented by Seth Snyder of the Argonne National Laboratory, reviewed development and performance of a novel bioreactor incorporating electrodeionization to simultaneously produce and separate products from both enzymatic and microbially mediated reactions. The sixth paper, " Optimization of Xylose Fermentation in Spent Sulfite Liquor by Saccharomyces cerevisiae 259ST," presented by Steven Helle of the University of British Columbia, provided an overview of an approach to fermentation optimization utilized to identify key process variables limiting use of the SSL for commercial ethanol production. 

The basis utilized by Petrides et al.15 is 1500 kg of purified BHI per year. They indicate that this represents 10-15% of the world demand.17 In essence, the following downstream steps are involved in sequence during synthetic BHI production. The fermentation step (not a downstream step) is also included to provide some continuity. The steps are fermentation, cell harvesting, cell disruption, inclusion body recovery, inclusion body solubilization, enzymatic conversion, refolding, sulfitolysis, CNBr cleavage, final purification steps, and crystallization. In the flow chart provided by Petrides et al.15, a surge tank separates the upstream from the downstream processes. This tank is in between the fermentor and the downstream processing steps. 

Heterofermentative LAB have the capability to utilize high concentrations of fructose such that the mannitol concentration in the fermentation broth could reach more than 180g/L, which is enough to be separated from the cell-free fermentation broth by cooling crystallization. Lactic and acetic acids can be recovered by electrodialysis (Soetaert et al., 1995). The enzyme mannitol dehydrogenase responsible for catalyzing the conversion of fructose to mannitol requires NADPH (NADH) as cofactor. Thus, it is possible to develop a one-pot enzymatic process for production of mannitol from fructose if a cost-effective cofactor regeneration system can be developed (Saha, 2004). The heterofermentative LAB cells can be immobilized in a suitable support, and... 

In the future, novel developments of liquid membranes for biochemical processes should arise. There are several opportunities in the area of fermentation or cell culture, for the in situ recovery of inhibitory products, for example. Another exciting research direction is the use of liquid membrane for enzyme encapsulation so that enzymatic reaction and separation can be combined in a single step. Chapter 6 by Simmons ial- (49) is devoted to this technique. The elucidation of fundamental mechanisms behind the liquid membrane stability is essential, and models should be developed for the leakage rate in various flow conditions. Such models will be useful to address the effect of parameters such as flow regime, agitation rate, and microdroplet volume... 

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