Production of cellulases and xylanases under catabolic repression conditions from mutant PR-22 of Cellulomonas flavigena |
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Authors: | Rojas-Rejn Oscar A Poggi-Varaldo Hctor M Ramos-Valdivia Ana C Martnez-Jimnez Alfredo Cristiani-Urbina Eliseo de la Torre Martnez Mayra Ponce-Noyola Teresa |
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Institution: | 1.Departamento de Biotecnología y Bioingeniería, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, 07300, Zacatenco, DF, Mexico ;2.Instituto de Biotecnología UNAM, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Morelos, Mexico ;3.Escuela Nacional de Ciencias Biológicas del IPN, Prolongación Carpio y Plan de Ayala, 11340, Plutarco Elías Calles, DF, Mexico ;4.Centro de Investigación en Alimentación y Desarrollo, Carretera La Victoria Km 0.6, 83304, Hermosillo, Sonora, Mexico ; |
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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. |
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