摘要:

AbstractThe microscopic green alga,Scenedesmus obliquus, was used in a semicontinuous culture system for the tertiary treatment of urban wastewater, with the simultaneous production of usable biomass. Partial biomass recycling was used to increase the productivity of the system by overcoming the limits imposed by the low maximal growth rate of the alga. The biomass to be recycled was collected by simple gravity settling of the removed culture.The culture system was operated at different dilution rates and its productivity measured at each rate. An evaluation of the crude nutrient composition of the algae produced at each dilution rate was also carried out.The system was found to operate stably at dilution rates of up to 0.8 day−1which represents a 20% net increase over the maximum dilution rate allowed under the same conditions in a system without recirculation. The composition of the biomass produced varied little over a range of dilution rates, which may be of relevance to its projected end‐use.The study indicated that such a system can exploit available light to the full and should be of particular value for the treatment of low‐strength wastes such as we emp

ISSN:0006-3592    

DOI:10.1002/bit.260310502

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

年代:1988

数据来源: WILEY

摘要:

AbstractThermophilic organisms offer many potential advantages for biotechnological processes; however, realization of the promise of thermophiles will require extensive research on bacterial thermophily and high‐temperature cultivation systems. This article describes a novel bioreactor suitable for precise studies of microbial growth and productivity at temperatures up to 260°C and pressures up to 350 bar. The apparatus is versatile and corrosion resistant, and enables direct sampling of both liquids and gases from a transparent culture vessel without altering the reaction conditions. Gas recirculation through the culture can be controlled through the action of a magnetically driven pump. Initial studies in this bioreactor ofMethanococcus jannaschii, an extremely thermophilic methanogen isolated from a deep‐sea hydrothermal vent, revealed that increasing the pressure from 7.8 to 100 bar accelerated the production of methane and cellular protein by this archaebacterium at 90°C, and raised the maximum temperature allowing growth from 90 to 92°C. Further increases in pressure had little effect on the growth rate a

ISSN:0006-3592    

DOI:10.1002/bit.260310503

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

年代:1988

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260310504

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

年代:1988

数据来源: WILEY

摘要:

AbstractA novel two‐stage anaerobic process for the microbial conversion of cellulose into biogas has been developed. In the first phase, a mixed population of rumen bacteria and ciliates was used in the hydrolysis and fermentation of cellulose. The volatile fatty acids (VFA) produced in this acidogenic reactor were subsequently converted into biogas in a UASB‐type methanogenic reactor.A stepwise increase of the loading rate from 11.9 to 25.8 g volatile solids/L reactor volume/day (g VS/L/day) did not affect the degradation efficiency in the acidogenic reactor, whereas the methanogenic reactor appeared to be overloaded at the highest loading rate. Cellulose digestion was almost complete at all loading rates applied. The two‐stage anaerobic process was also tested with a closed fluid circuit. In this instance total methane production was 0.438 L CH4g VS added, which is equivalent to 98% of the theoretical value. The application of rumen microorganisms in combination with a high‐rate methane reactor is proposed as a means of efficient anaerobic degradation of cellulosic residues to methane. Because this newly developed two‐phase system is based on processes and microorganisms from the ruminant, it will be referred to as “Rumen Derived Anaerobic Digestion” (RU

ISSN:0006-3592    

DOI:10.1002/bit.260310505

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

年代:1988

数据来源: WILEY

摘要:

AbstractFed‐batch cultures were performed to maximize the α‐amylase activity in a bioreactor. Kinetic equations containing a catabolite repression effect were used to model the enzyme formation fromBacillus amyloliquefaciens. Fed‐batch culture experiments were performed using maltose to implement the optimal feeding strategy. Optimal fed‐batch culture based on sequential parameter estimation was performed successfully using off‐line analysis while the fermentation was in progress. The enzyme activity from the fed‐batch culture employing maltose was higher than that of the batch culture by 60%. Enzyme production using starch showed similar trends to those obtained u

ISSN:0006-3592    

DOI:10.1002/bit.260310506

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

年代:1988

数据来源: WILEY

摘要:

AbstractExtracts of solid‐state cultures ofPenicillium capsulatumgrown on beet pulp exhibit cellulolytic, hemicellulolytic, and pectinolytic activities. Such extracts catalyzed extensive solubilization of untreated beet pulp. The effects of pH, temperature, and endproducts on the saccharification process were investigate

ISSN:0006-3592    

DOI:10.1002/bit.260310507

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

年代:1988

数据来源: WILEY

摘要:

AbstractA specific ligand bound polymer has been synthesized for the purpose of purification and stabilization of trypsin, an easily autodigestible enzyme. The affinity polymer was formed by copolymerizingN‐acryloyl‐m‐aminobenzamidine, a strong trypsin inhibitor, and acrylamide in the absence of oxygen. Kinetic studies on the trypsin inhibition revealed that there was a strong binding between this enzyme and the polymer and the mechanism was of a competitive manner with an inhibition constant of 0.6 × 10−3M. Such an affinity polymer was also very effective in preventing trypsin from auto‐digestion at 4°C.Based on this finding and the principle of cross flow filtration, a new process has been developed for purification of trypsin from a solution containing chymotrypsin. The experimental data indicated that trypsin was bound to the polymer (MW>105) and remained in the retentate while unbound chymotrypsin was collected in the filtrate. This purification process has a capability of recovering 98% pure trypsin a

ISSN:0006-3592    

DOI:10.1002/bit.260310508

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

年代:1988

数据来源: WILEY

摘要:

AbstractSteam explosion after sulphur dioxide impregnation of wood chips is an effective method for improving the enzymatic digestibility of cellulose in the softwoodPinus radiata. Digestibility of pretreated fiber was progressively increased by altering the conditions of steam explosion. With increasing digestibility, there was an observed increase in fiber porosity as measured by the solute exclusion technique. Accessible pore volume and accessible surface area to a 5‐nm dextran probe positively correlated with both 2‐ and 24‐h digestion yields from pretreated fiber. The increase in accessibility was probably the result of hemicellulose extraction and lignin redistribution. A subsequent loss in accessibility, brought about by structural collapse or further lignin redistribution, resulted in a corresponding loss in digestibility. It appears that steam explosion increases cellulose digestibility inP. radiataby increasing fiber por

ISSN:0006-3592    

DOI:10.1002/bit.260310509

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe water activity (aw) of substrates has been related to the mycelial growth and the sporogenesis of two molds. In the absence of other limiting factors, optimalawvalues were determined for growth and sporogenesis as 0.99 and 0.98, respectively, forTrichoderma viride TSand 0.97 and 0.96 forPenicillium roqueforti. In all cases, the accuracy of the optimal value would justify the regulation of this parameter. A model was proposed which establishes a relationship between the mycelial growth and the water activity value of the substrate.

ISSN:0006-3592    

DOI:10.1002/bit.260310510

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe implication of the possible existence of differences in the times required for plasmid‐bearing and non‐plasmid‐bearing microorganisms to adjust their metabolic activities to step changes in their environment is examined. This adaptability difference suggests the possibility of maintaining an engineered strain in continuous culture by transient operation. It is shown for the case where adaptability is neglected that no cycling strategy will prevent the washout of the engineered strain, but the addition to the model of a time delay in substrate utilization can result in coexistence upon cycling. Numerical simulations of cycling in feed substrate concentration are carried out to illustrate the concept Operating diagrams are also constructed to indicate the conditions under which washout of the plasmid bearing strain can be prev

ISSN:0006-3592    

DOI:10.1002/bit.260310511

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

年代:1988

数据来源: WILEY