A simple and effective method of treatment of lignocellulosic material was used for the preparation of corn cob for the production
of 2,3-butanediol byKlebsiella oxytoca ATCC 8724 in a simultaneous saccharification and fermentation process. During the treatment, lignin, and alkaline extractives
were solubilized and separated from cellulose and hemicellulose fractions by dilute ammonia (10%) steeping. Hemicellulose
was then hydrolyzed by dilute hydrochloric acid (1%, wJv) hydrolysis at 100°C at atmospheric pressure and separated from cellulose
fraction. The remaining solid, with 90% of cellulose, was then used as the substrate. A butanediol concentration of 25 g/L
and an ethanol concentration of 7 g/L were produced byK. oxytoca from 80 g/L of corn cob cellulose with a cellulase dosage of 8.5 IFPU/g corn cob cellulose after 72 h of SSF. With only dilute
acid hydrolysis, a butanediol production rate of 0.21 g/L/h was obtained that is much lower than the case in which corn cob
was treated with ammonia steeping prior to acid hydrolysis. The butanediol production rate for the latter was 0.36 g/L/h. 相似文献
Rotary biofilm contactor (RBC) is a reactor consisting of plastic discs that act as supports for micro-organisms. The discs are mounted on a horizontal shaft and placed in a medium-containing vessel. During nitrogen-rich growth phase, mycelia ofRhizopus oryzae ATCC 20344 grew on and around the discs and formed the “biofilm” of self-immobilized cells on the surface of the plastic discs. During the fermentation phase, the discs are slowly rotated, and the biofilms are exposed to the medium and the air space, alternately. With RBC, in the presence of CaCO3,Rhizopus biofilm consumes glucose and produces fumaric acid with a volumetric productivity of 3.78 g/L/h within 24 h. The volumetric productivity is about threefolds higher with RBC than with a stirred-tank fermenter with CaCO3. Furthermore, the duration of fermentation is one-third of the stirred-tank system. The immobilized biofilm is active for over a 2-wk period with repetitive use without loss of activity.
Airlift loop reactors with porous spargers were investigated and used in the process of fumaric acid production byRhizopus oryzae ATCC 20344. In order to enhance oxygen mass transfer, which is very important for organic acid production, two kinds of porous spargers (stainless steel membrane tube and porcelain tube) were examined. Gas holdup, liquid circulation velocity, mixing time, bubble size, and bubble rise velocities were measured in a 50 L rectangular airlift loop reactor with different ratios of the cross-sectional area of the riser and downcomer. The local volumetric mass transfer coefficient (KLa) was also measured in the gas sparger zone. The results indicated that high KLa and excellent hydrodynamics can be obtained in the airlift loop reactor with a porous sparger. A 10 L laboratory airlift loop reactor was employed for the fumaric acid fermentation. Results showed that the turbulence of two-phase flow in the airlift loop reactor not only produced favorable conditions for mass transfer, but was also useful for forming and suspending small, well-distributed mycelial pellets (1ç2 mm). A production rate of up to 0.814 g/L/h and efficiency yield of 50.1% (w/w) was obtained in the airlift loop reactor. The performance was compared with the typical stirred tank fermentor fermentation results.
Aspergillus niger NRRL3 was cultivated in a moist wheat bran and ground corncob solid medium supplemented with inorganic minerals for the production
of cellobiase (β-1,4-glucosidase, EC 3.2.1.21). With this method, A. niger NRRL3 was able to produce a high concentration of cellobiase (215 IU/gofsolid substrate) after 96 h of incubation. Temperature
and moisture content affected final cellobiase titers. The best conditions for cell obiase production from solid substrate
by A. niger NRRL3 were determined to be 70% moisture and 35°C. 相似文献
Based on the theory of inverse eigenvalue problem, a correction of an approximate model is discussed, which can be formulated
as NX=XΛ, where X and Λ are given identified modal and eigenvalues matrices, respectively. The solvability conditions for a symmetric skew-Hamiltonian
matrix N are established and an explicit expression of the solutions is derived. For any estimated matrix C of the analytical model, the best approximation matrix to minimize the Frobenius norm of C − N is provided and some numerical results are presented. A perturbation analysis of the solution is also performed, which has scarcely appeared in existing literatures.
Supported by the National Natural Science Foundation of China(10571012, 10771022), the Beijing Natural Science Foundation
(1062005) and the Beijing Educational Committee Foundation (KM200411232006, KM200611232010). 相似文献
Applied Biochemistry and Biotechnology - The ability of the resting cells ofBrevibacterium sp. B2D, a flocculent strain, to convert fumaric acid tol-malic acid was investigated under different... 相似文献
The dynamic buckling problem of elastic bars subjected to axial impact has been investigated by many authors in different
ways. In this paper the problem, in which the elastic bars are assumed to be ideally straight, is reformulated in connection
with the bifurcation due to the stress wave propagation. The example of a semi-infinite elastic bar is used for illustration. 相似文献