摘要:

AbstractOptimal operation of repeatedly fed‐batch was determined by the continuous maximum principle for the constant yield case. The objective of maximum cell productivity for a fixed cell concentration was achieved by finding the substrate feeding policy that minimized the processing time. Analytical criteria for the optimal filling policy show that an exponential policy is optimum when the specific growth rate has a maximum, and also that operation in the simple repeated batch mode is optimum when the specific growth rate is monotonic increasing. Comparisons between optimal repeated fed‐batch culture and other modes of operation were made for the case of substrate‐inhibited growth. Cell productivity by repeated fed‐batch exceeds both batch and continuous operation for the case of low residual substrate concen

ISSN:0006-3592    

DOI:10.1002/bit.260230202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractCandida Kruseihas a optimum growth temperature of 37°C on SASOL ethanol‐isopropanol mixture. The organism was unable to grow on isopropanol, but oxidized it partially to acetone in the presence and absence of ethanol. Growth at 40°C in the alcohol mixture was slightly faster than at 30°C over an ethanol concentration range of 0.43 to 3.6% (v/v), although at both temperatures the growth rate declined continuously with increasing concentration. At an ethanol concentration greater than 3.6% (v/v), the mixture was much more inhibitory to growth at 40 and 30°C. The inhibitory effect was due to the ethanol rather than the isopropanol. Metabolites such as acetate, acetaldehyde, and ethyl acetate accumulated in the medium, but the degree of accumulation depended upon the temperature and alcohol mixture concentration. At 40°C, acetaldehyde and acetate accumulated to a greater extent than 30°C on a 4.0% (v/v) synthetic alcohol mixture and this may also cause the greater inhibition at this temperature. The alcohol mixture is unsuitable for single cell protein (SCP) production in batch culture because of the low cell densities observed at all alcohol concent

ISSN:0006-3592    

DOI:10.1002/bit.260230203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThe dynamic oxygen electrode method for measuringKLarequires the use of a dynamic process model. Six models from the literature are described and compared with respect to their accuracy and ease of use. It is shown theoretically that for sufficient accuracyKLashould be less than the inverse electrode response time. Experimental measurements demonstrate their application to viscous and nonviscous systems. The liquid diffusion film is shown to cause an important measurement lag that can be accounted for by a first‐order time delay. Investigation on the influence of the experimental starting conditions show the importance of the gas and hold‐up dynamics. A new method is proposed to simplify theKLacalculation and to eliminate errors caused by starting conditions. This method, which accounts for gas, film, and electrode dynamical effects, requires only a simple semilog plot of the response d

ISSN:0006-3592    

DOI:10.1002/bit.260230204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractRaw cassava root starch was transformed into ethanol in a one‐step process of fermentation, in which are combined the conventional processes of liquefaction, saccharification, and fermentation to alcohol.Aspergillus awamoriNRRL 3112 andAspergillus nigerwere cultivated on wheat bran and used as Koji enzymes. CommercialA. nigeramyloglucosidase was also used in this experiment. A raw cassava root homogenate–enzymes–yeast mixture fermented optimally at pH 3.5 and 30°C, for five days and produced ethanol. Alcohol yields from raw cassava roots were between 82.3 and 99.6%. Fungal Koji enzymes effectively decreased the viscosity of cassava root fermentation mashes during incubation. CommercialA. nigeramyloglucosidase decreased the viscosity slightly. Reduction of viscosity of fermentation mashes was 40, 84, and 93% by commercial amyloglucosidase,A. awamori, andA. nigerenzymes, respectively. The reduction of viscosity of fermentation mashes is probably due to the hydrolysis of pentosans by Koji e

ISSN:0006-3592    

DOI:10.1002/bit.260230205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractIt has been shown both theoretically and experimentally that interphase nitrogen transport may have a significant influence on the rate of interphase oxygen transport, and thereby also on the value of the volumetric mass transfer coefficient of oxygen,kla, determined in mechanically agitated bubble fermentors using the variants of dynamic method presented in the literature. The experiments were carried out in 1MKCI solution at five stirrer frequencies and two gas inlet levels. The gas interchanges were performed either without interrupting the aeration and agitation of the charge (A) or with the aeration and agitation of the charge turned on at the same time (B). The applied variants of the interchange were N2→ O2→, O2→ N2, N2→ air, air→ N2, O→ O2, and O→ air. In the two last variants the oxygen dissolved in the charge was removed by reacting with sulfite ions. Theklavalues calculated by allowing for the nitrogen transport for procedure A were approximately equal to the values obtained by disregarding the nitrogen transport, whereas those for procedure B were higher (up to 40%), than the values obtained disregarding the nitro

ISSN:0006-3592    

DOI:10.1002/bit.260230206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThe determination of growth constant ofAspergillus nigerwere obtained for semisolid cultures on cassava flour,Manihot esculenta, as a sole carbon source. As a consequence, a technique was developed that consisted of the use of a packed‐bed microfermentor with a working volume of 16 cm3. The bed consisted of gelatinized and granulated cassava flour containing mineral nutrients and mold spores. The carbon dioxide produced during the respiration was drawn off with a current of air and then absorbed in a solution of sodium hydroxide. The absorption of CO2,P, was correlated with the specific growth rate μ, by means of the equationP=Keμt, wheretis time andKis a constant. Ammonium nitrogen was used as a limiting substrate and its concentration was varied from 0.039 to 2.5% in dry base. The maximum growth rate, μmax, and the saturation constant,Ks, were 0.31 hr−1and 0.065 mmol (NH4)2SO4/g total dry solids. Substrate inhibition was presented and the constantkigave a value of 1.5 mmol (NH4)2SO4/g total dry solids. The proposed method is highly recommended for the evaluation of the semisolid fermentation of molds and for strictly aerobic bacteria and yeasts. It can be used especially in the evaluation of the growth of microorganisms on peanut shells, coffee residues, sugar cane bagasse, and other agricultural

ISSN:0006-3592    

DOI:10.1002/bit.260230207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThe viscosity, density, and sedimentation characteristics of suspensions of whole and mechanically disrupted yeast cells were measured. Mechanical disruption increases the suspension viscosity and its non‐Newtonian behavior. Experiments showed a good correlation between laboratory‐ and industrial‐scale centrifugation re

ISSN:0006-3592    

DOI:10.1002/bit.260230208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThe filamentous fungus,Rhizopus nigricans, was immobilized in polyacrylamide, alginate, and agar gels and its ability to 11α‐hydroxylate progesterone was examined. No activity was detected using polyacrylamide gel but both agar and alginate gels have proved capable of hydroxylation. Agar gels displayed faster rates and higher yields. It was possible to induce hydroxylase synthesis within agar and alginate gels, and microscopical examination provided evidence for hyphal growth within these gels. The concept of increased biomass was used to explain the observed increase in the rates of hydroxylase activity of the immobilized cells. Conversely, hyphal overcrowding was postulated for the rapid inactivation observed under some operating conditio

ISSN:0006-3592    

DOI:10.1002/bit.260230209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractSynthesis of a peptide bond is suggested to be enzymatically catalysed in a biphasic system “water–water‐immiscibleorganic solvent”. The pH dependence of the apparent equilibrium constant is studied for synthesis ofN‐acetyl‐L‐tryptophanyl‐L‐leucine amide fromN‐Acet‐Trp andL‐Leu‐NH2. The reaction was performed in the biphasic system ethyl acetate plus water [from 2 to 2% (v/v)] in the presence of α‐chymotrypsin. The suggested approach is preparative value: with the stoichiometric ratio of the reagents, [N‐Acet‐L‐Trp] = [L‐Leu‐NH2] = 2 × 10−3M, the yield is practically 100% (in water, with other conditions be

ISSN:0006-3592    

DOI:10.1002/bit.260230210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractAn enzyme which catalyzes the synthesis of cephalexin fromD‐α phenylglycinemethylester (PGM) and 7‐amino‐3‐desacetoxy‐cephalosporanic acid (7‐ADCA) was prepared fromXanthomonas citri(IFO 3835) and partially purified 30‐fold by ammonium sulfate fractionation, DEAE‐cellulose, and Sepharose‐4B column chromatography. TheKmvalues for 7‐ADCA, PGM, and cephalexin were determined as 11.1, 2.1, and 1.61 mM, respectively. The enzymatic cephalexin synthesis follows the reversible bi‐uni reaction kinetics. The equilibrium constant is influenced by the initial mole ratios of 7‐ADCA and PGM. The cephalexin hydrolysis is catalyzed by the same cephalexin synthesizing enzyme, but methanol does not participate in the hydrolytic reaction. The amount of enzyme in the reaction mixture affects the initial rate but does not influence the equilibrium product concentration. This cephalexin‐synthesizing enzyme was immobilized onto several adsorbents. Among these, Kaolin and bentonite showed a higher retention of enzyme activity and stability for reuse. The immobilized‐enzyme reaction kinetics were investigated and compared with those of the soluble enzyme. A rate expression for the enzymatic synthesis of cephalexin was derived. The results of computer simulation showed good agreement w

ISSN:0006-3592    

DOI:10.1002/bit.260230211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY