摘要:

Levan is a fructose polymer with potential importance as fructose source or thickening agent in food technology in case that it could be produced in a simple and cheap process. Levan concentrations of up to 42.5 g/L and a yield from fructose of 032 g/g were obtained with a new flocculent mutant ofZymomonas mobilis. Asucrose concentration of 250 g/L, pH‐values around 5.0 and temperatures of 27 to 30 °C were optimal. Higher pH‐values and high starting concentrations of levan caused hydrolysis of the polymer by the bacterium itself. However, adding levan up to 1.5 g/L led to nearly 40%increase of the levan synthesis. Sorbitol also increased levan formation due to a decrease of sucrose and levan hydrolysis. Presumably by induction of the levansucrase, fructose addition caused a higher levan yield too. In continuous operation, a levan productivity of 16 g/L.h and an ethanol productivity of 26.3 g/L.h resulted. That was 5 to 12 times, respectively the productivity of batch processes. These results are interpreted as very promising.

ISSN:0890-5436    

DOI:10.1080/08905439009549723

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0890-5436    

DOI:10.1080/08905439009549724

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The great advantage of producing optically pure D‐ or L‐amino acids from D,L‐5‐monosubstituted hydantoins by bioconversion is the fact that most of the substrates already racemize under reaction conditions and are totally converted to the optically pure amino acids. Three enzymes were shown to be involved in the production of L‐tryptophan from D,L‐5‐indolylmethylhydantoin inArthrobacter spec.DSM 3747 after growth in a medium containing the chemically synthesized D.L‐5‐indolyl‐3‐N‐methlylhydantoin as effective inducer. Besides a hydantoinase and a N‐carbamoyl‐L‐amino acid amidohydrolase, a 5‐indolylmethylhydantoin racemase was found and could be separated from the former enzymes by liquid‐liquid extraction and gel filtration.

ISSN:0890-5436    

DOI:10.1080/08905439009549725

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0890-5436    

DOI:10.1080/08905439009549726

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In biotechnological processes requiring a continuous or repeated substrate supply, an automatic control of the feed rate is desirable. This should be able to react appropriate on varying properties of the microorganisms, changes in substrate quality or other operating parameters.

ISSN:0890-5436    

DOI:10.1080/08905439009549727

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Bioengineering with respect to food technology Involves unit operations such as up‐ and downstream units, bioreactors, the modeling of reaction kinetics, heat and mass transport, energy and mass balance, and diverse material data. Process design, plant layout, and criteria for scale‐up, optimization, and control strategies are derived based upon these unit operations. For some typical processes, i. e. the isomerization of glucose and lipid interesterification, critical bioreactor design parameters are shown. Downstream operations and concepts for continuous processing featuring integration of reactor and downstream units are shown for the drying of microorganisms, acid fermentation, and lactose hydrolysis in an enzyme dialysis reactor.

ISSN:0890-5436    

DOI:10.1080/08905439009549728

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Pichia stipitis(CBS 5773) most efficiently ferments the sugar mixture from acid hydrolysed spent brewer's grains, whereby D‐xylose and D‐galactose (but not L‐arabinose) are consumed simultaneously, after the D‐glucose had been used up from the mixture. The key enzymes, xylose reductase (Xyl‐R) and xylitol dehydrogenase (Xit‐DH) are inducible and cannot be found in glucose‐grown cells. Purified Xyl‐R was shown to use both NADH and NADPH as coenzyme, and model simulations showed that under aerobic physiological conditions NADPH is preferred (95%), whereas under oxygen deficiency 85% of xylose are reduced by NADH. Xit‐DH seems to use only NAD+as coenzyme, and the reaction is competitively inhibited by NADH. According to the equilibrium constants for Xyl‐R (5,5.1091.Mol‐1) and for Xit‐DH (6,9.10‐11Mol.1‐1) the equlibria of both reactions are distinctly shifted to xylitol, which may be excreted into the medium, especially when in the absence of oxygen a surplus of NADH cannot be dehydrogenated.

ISSN:0890-5436    

DOI:10.1080/08905439009549729

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0890-5436    

DOI:10.1080/08905439009549730

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0890-5436    

DOI:10.1080/08905439009549731

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Effects of bovine serum albumin on the growth of hybridoma cells in an airlift loop reactor show the importance of protein concentration for the prevention of mechanical cell damage. To confirm the hypothesis that this is caused by a decrease turbulence of the medium, measurements of wall shear rate vectors with a newly developed electrochemical probe were carried out. The results of these measurements show that turbulence is reduced with increasing protein concentration. Thus, turbulence effects must be responsible for mechanical cell damage.

ISSN:0890-5436    

DOI:10.1080/08905439009549732

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor