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Cellulase Production
Published in Charles E. Wyman, Handbook on Bioethanol, 2018
Cellulase is an inducible enzyme system, and several compounds have been described as inducers. However, not all are true inducers, as they have never been shown to actually bind to an intracellular protein [29]. The natural inducer (which prevents cellulase biosynthesis repression) has not yet been identified, so the term inducer is used loosely. Cellulose, cellobiose, and lactose effectively induce the cellulase complex at high concentrations, whereas sophorose is effective even at very low concentrations. The cellulases elicited by T. reesei on cellulose or lactose as the sole carbon source contain a complete and well-balanced cellulase complex, whereas some other sugars, such as sophorose as a sole carbon source, yield a less complete complement of the cellulase components. Nevertheless, all T. reesei cellulases, irrespective of the inducer, contain sufficient amounts of all necessary components to hydrolyze insoluble cellulose.
Mechanism of Anaerobic Degradation of Aromatic Compounds in Texas Lignite by Bacteria
Published in Donald L. Wise, Bioprocessing and Biotreatment of Coal, 2017
G. Fuchs, A. Kröger, Rudolf K. Thauer
The pathway of degradation has been investigated with one denitrifying Pseudomonas sp. and phenol as the substrate (Fig. 12.2). The first step appears to be carboxylation of phenol to 4-hydroxybenzoate, catalyzed by an inducible enzyme tentatively named phenol carboxylase (I). Cell extracts also contained an inducible 4-hydroxybenzoyl CoA synthetase (II), which activates the aromatic acid. This is followed by reductive dehydroxylation of the para-hydroxyl group, resulting in benzoyl CoA formation; this enzyme, 4-hydroxybenzoyl CoA reductase (dehydroxylating) (III), is also inducible. Finally, benzoyl CoA is reduced to a not-yet-defined CoA thioester of cyclohexanecarboxylate or cyclohexenecarboxylate; this reaction (IV) remains to be studied. We assume that the reduction product is further degraded via β-oxidation, essentially to acetylcoenzyme A, possibly via pimelyl-CoA as intermediate. The analogous degradation of cyclohexanol has been shown to proceed via the sequence of reactions shown in Fig. 12.3.
Performance Characteristics of an Activated Sludge System When Nitrate is the Sole Source of Nitrogen
Published in John W. Bell, Proceedings of the 45th Industrial Waste Conference May 8, 9, 10, 1990, 1991
Nannette Corey, James M. Montgomery, Larry Benefield
The key enzyme in nitrate respiration is nitrate reductase which reduces nitrate to nitrite. Actually two different nitrate reductase enzymes have been found to be involved in nitrate respiration.4 These enzymes have been classified as nitrate reductase A and nitrate reductase B. Nitrate reductase A seems to always play a role in nitrate respiration, but the function of nitrate reductase B is different in different bacteria and little information is available on the basic properties of this particular enzyme. In general, nitrate reductase A is an inducible enzyme which is formed only in the absence of oxygen and in the presence of nitrate. Under aerobic conditions the formation of both nitrate reductase A and nitrate reductase B is repressed.
Optimization of process parameters for naringinase production by Aspergillus tubingensis UA13 and pilot scale-up study
Published in Preparative Biochemistry & Biotechnology, 2022
Xin-Ke Xia, Yuan-E. Zhang, Sheng-Jiao Lei, Biao Hu, Cai-Xia Fu
Inducers were essential for biosynthesis of the inducible enzyme, naringinase. A variety of inducers, such as naringin, naringenin, rhamnose, pomelo peel powder, rutin, hesperidin and etc.,[16–18] have been reported for extracellular naringinase production. Pomelo peel powder is a potential source because it is economical and easily available. In this research, the effects of naringin and pomelo peel powder on naringinase production were explored and the results illustrated that naringin is a more effective inducer for Aspergillus tubingensis UA13 than pomelo peel powder. This is consistent with Kumar’s [19] finding that naringin substantially improved naringinase production while compared with rhamnose, naringenin, rutin, hesperidin and other inducers.
Enhanced β-mannanase production by Bacillus licheniformis by optimizing carbon source and feeding regimes
Published in Preparative Biochemistry & Biotechnology, 2021
Yangcun Sun, Xiaohang Zhou, Wen Zhang, Xue Tian, Wenxiang Ping, Jingping Ge
In most cases, β-mannanase is an inducible enzyme that is secreted by microorganisms;[23] only rarely is β-mannanase located within the cell or is associated with the cell membrane and serves as a constitutive enzyme.[24] Therefore, for the microbial synthesis of most β-mannanases, appropriate inducers, such as mannan or mannan oligosaccharides,[25] must be added as a carbon source to the culture medium. In the absence of these carbon sources, the expression level of enzymes is very low and can only maintain basal bacterial growth.[26] In addition to mannan and its hydrolytic products, cellulose[27] or even monosaccharides such as glucose[28] can also be used as inducers to effectively improve the production level of certain microbial β-mannanases. Polysaccharides (such as dextrin, starch, konjaku powder and guar gum) can significantly promote cellular metabolism,[29] and monosaccharides such as glucose and maltose significantly affect cell growth.[26] While polysaccharides are used as carbon sources, adding a certain amount of glucose can promote the growth of bacteria.[30]
Optimization of extracellular lipase production by halotolerant Bacillus sp. VITL8 using factorial design and applicability of enzyme in pretreatment of food industry effluents
Published in Preparative Biochemistry & Biotechnology, 2020
Lavanya Balaji, Jabeena Thaz Chittoor, Gurunathan Jayaraman
Lipases are inducible enzymes and generally require the presence of lipid sources such as oil, triglycerides, fatty acids, tweens, bile salts and glycerol as its inducer.[8] Hence, in the present study, different oils such as olive oil, coconut oil, castor oil, groundnut oil, palm oil, and sunflower oil were used for studying their effect on lipase production. Among these, olive oil was found to influence higher lipase production of about 217.9 ± 2.8 U mL−1 (Figure 1). In the absence of olive oil the organism did not produce any detectable amount of lipase, in agreement to the fact that the lipase produced by Bacillus sp. VITL8 is an inducible enzyme. This was followed by sunflower oil (211.4 ± 0.7 U mL−1), groundnut oil (209.8 ± 4.2 U mL−1), castor oil (195.2 ± 2.1 U mL−1), coconut oil (143.2 ± 1.4 U mL−1) and palm oil (97.3 ± 6.4 U mL−1). Thus, olive oil was selected as the best inducer for lipase production. It was also shown that Aspergillus niger and Bacillus coagulans produce the highest yield of lipase only in the presence of olive oil.[20]