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- Kovacs, Krisztina, et al.
(author)
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Trichoderma atroviride mutants with enhanced production of cellulase and beta-glucosidase on pretreated willow
- 2008
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In: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 43:1, s. 48-55
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Journal article (peer-reviewed)abstract
- Trichoderma atroviride mutants were developed by using N-methyl-N'-nitro-N-nitrosoguanidine (NTG) treatment and UV-Iight followed by a semiquantitative plate clearing assay on Walseth-cellulose/agar plates. The parent strain of the mutants was an isolate from the Amazonas basin (TUB F-1505), whose identity was established by ITS 1 and 2 and tef1 gene sequence analysis. Strain F-1505 proved to be the most promising extracellular cellulase producer among 150 wild-type Trichoderma in a screening program performed in shake flask fermentation on pretreated willow. Reducing sugar content, soluble protein, filter paper cellulase activity (FPA), beta-glucosidase activity and endoglucanase activity of the fermentation broths of the mutant strains were measured in both shake flask and lab-scale fermenters and compared with Trichoderma reesei Rut C30. Also, hydrolytic capacities of fermentation supernatants of T reesei Rut C30, the parent strain (F-1505) and the best mutants were compared on pretreated willow as carbon source and hydrolysis substrate. The T atroviride mutants produced high levels of extracellular cellulases as well as beta-glucosidase, rendering the need for beta-glucosidase supplementation in hydrolysis of cellulose or pretreated willow unnecessary. On the contrary, beta-glucosidase supplementations were essential in order to obtain good glucose yields for all other cellulase preparations tested.
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| 2. |
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| 3. |
- Revstedt, Johan, et al.
(author)
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Influence of impeller type on the flow and mixing in a stirred reactor
- 2000
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In: AIChE Journal. - : Wiley. - 1547-5905 .- 0001-1541. ; 46:12, s. 2373-2382
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Journal article (peer-reviewed)abstract
- Large eddy simulations (LES) of a stirred reactor with a liquid volume of 0.64 m3 were performed. The tank was stirred by either two standard Rushton impellers or two Scaba 6SRGT impellers. The LES can provide details of the flow field that cannot be obtained with so‐called Reynolds‐averaged equations and the corresponding models. The unsteady spatially filtered incompressible Navier‐Stokes equations were solved together with a transport equation for the concentration of an inert additive using a multigrid finite difference code with a staggered grid. The unresolved turbulent scales were modeled using a scale similarity model. The aim of this investigation has been to study the influence of impeller type on the flow structure and scalar transport. The results show that, compared at equal power input, the center plane velocities and the volume flow in the impeller stream do not differ much for the impeller types. Also, for the 6SRGT the periodic fluctuations associated with the blade passing is less pronounced
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