title: Production of cellulases and xylanases under catabolic repression conditions from mutant PR-22 of Cellulomonas flavigena.
abstract: Derepressed mutant PR-22 was obtained by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) mutagenic treatment of Cellulomonas flavigena PN-120. This mutant improved its xylanolytic activity from 26.9 to 40 U mg(-1) and cellulolytic activity from 1.9 to 4 U mg(-1); this represented rates almost 2 and 1.5 times higher, respectively, compared to its parent strain growing in sugarcane bagasse. Either glucose or cellobiose was added to cultures of C. flavigena PN-120 and mutant PR-22 induced with sugarcane bagasse in batch culture. The inhibitory effect of glucose on xylanase activity was more noticeable for parent strain PN-120 than for mutant PR-22. When 20 mM glucose was added, the xylanolytic activity decreased 41% compared to the culture grown without glucose in mutant PR-22, whereas in the PN-120 strain the xylanolytic activity decreased by 49% at the same conditions compared to its own control. Addition of 10 and 15 mM of glucose did not adversely affect CMCase activity in PR-22, but glucose at 20 mM inhibited the enzymatic activity by 28%. The CMCase activity of the PN-120 strain was more sensitive to glucose than PR-22, with a reduction of CMCase activity in the range of 20-32%. Cellobiose had a more significant effect on xylanase and CMCase activities than glucose did in the mutant PR-22 and parent strain. Nevertheless, the activities under both conditions were always higher in the mutant PR-22 than in the PN-120 strain. Enzymatic saccharification experiments showed that it is possible to accumulate up to 10 g l(-1) of total soluble sugars from pretreated sugarcane bagasse with the concentrated enzymatic crude extract from mutant PR-22.
authors.affiliation: Departamento de Biotecnología y Bioingeniería, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, 07300, Zacatenco, DF, Mexico.
authors.forename: Oscar A
authors.initials: OA
authors.lastname: Rojas-Rejón
authors.forename: Héctor M
authors.initials: HM
authors.lastname: Poggi-Varaldo
authors.forename: Ana C
authors.initials: AC
authors.lastname: Ramos-Valdivia
authors.forename: Alfredo
authors.initials: A
authors.lastname: Martínez-Jiménez
authors.forename: Eliseo
authors.initials: E
authors.lastname: Cristiani-Urbina
authors.forename: Mayra
authors.initials: M
authors.lastname: de la Torre Martínez
authors.forename: Teresa
authors.initials: T
authors.lastname: Ponce-Noyola
mesh_terms: D018533:Biomass; D002475:Cellobiose / Q000378:metabolism; D002480:Cellulase / Q000096:biosynthesis*; D040143:Cellulomonas / Q000201:enzymology* / Q000235:genetics; D002482:Cellulose / Q000378:metabolism; D003470:Culture Media; D043364:Endo-1,4-beta Xylanases / Q000096:biosynthesis*; D005947:Glucose / Q000378:metabolism; D007218:Industrial Microbiology; D009154:Mutation
chemical_list: D003470:Culture Media; D002475:Cellobiose; D002482:Cellulose; C027433:bagasse; D002480:Cellulase; C019826:carboxymethylcellulase; D043364:Endo-1,4-beta Xylanases; D005947:Glucose
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