Enzymes in Biomass Conversion - ACS Publications - American

Chapter 31

Biotechnological Potential and Production of Xylanolytic Systems Free of Cellulases

Downloaded by UNIV OF ROCHESTER on May 4, 2017 | http://pubs.acs.org Publication Date: April 30, 1991 | doi: 10.1021/bk-1991-0460.ch031

Peter Biely Institute of Chemistry, Slovak Academy of Sciences, Bratislava, Czechoslovakia

Xylanolytic enzymes free of cellulases can be applied in the pulp and paper, textile, and food industries and in basic research. However, most microorganisms grown under natural conditions produce both xylanases and cellulases. Strategies to produce xylanolytic systems free of cellulases are elimination of cellulase activity by separation or inhibit ion, selection and construction of cellulase-negative strains, and finding conditions for separate production of xylanolytic systems by cellulolytic strains. The last five years have seen growing interest in microbial xylanolytic systemsfreeof cellulases. The reason is that such systems can be applied in processes where xylan is to be removed from cellulose with cellulose fiber length being preserved. These in clude mainly the purification of pulp and modification of its paper-making properties. In 1984 Pake and Jurasek (7) suggested the application of xylanasesfreeof cellulases for removal of xylanfromchemical pulp in the production of high-quality dissolving pulp. The intention was to replace the ecologically harmful alkaline extraction of heirricellulose with an enzymic treatment, leading to a mixture of fermentable sugars instead of polluting waste liquors. Xylanolytic enzymes attracted further attention after Viikari et al. (2,3) announced that xylanases may facilitate chemical extractibility of lignin from crude pulp by their hydrolysis of xylan in lignin-xylan complexes, leading to a significant saving of chemicals used for bleaching. Other important information was that a controlled xylanase treatment of pulp enhances its beatability and binding ability, thus affecting its paper-making properties (4,5). The pulp and paper industry's inter est in xylanolytic enzyme systems should increase with growing pressure of govern ments and "green" initiatives to reduce or replace the ecologically harmful technologies of pulp bleaching. In addition to the pulp and paper industry, xylanasesfreeof cellulases may be ap plied in the textile and food industries and in basic research. They can be applied to gether with pectinases in the processing of plant fiber sources such as flax and hemp. Classicalfiberliberation is caused by natural retting in situ by microorganisms, lead ing to the removal of pectin and hemicellulose binding material. Pectinases are be lieved to play the main role in the process, but xylanases may also be involved. Re placement of slow natural retting, which is strongly dependent on weather conditions, by controlled enzyme retting using defined enzyme mixtures may lead to new fiber lib0097-6156/91/0460-0408$06.00/0 © 1991 American Chemical Society

Leatham and Himmel; Enzymes in Biomass Conversion ACS Symposium Series; American Chemical Society: Washington, DC, 1991.


31.

BIELY

Xylanolytic Systems Free of Cellulases

409

eration technology. Expected advantages of enzyme retting are high reproducibility, better yield, and higher fiber strength, caused by a higher degree of cellulose polymer ization (6). The application of xylanases in the food industry should not so strictly require the absence of cellulases. Xylanases can be used for modification of bakery products by affecting dough development (7) and by changing rheological properties of cooked rice (#). Xylanases have been used also in the starch and gluten processing industry. Treatment of flour slurries with xylanase decreases viscosity and allows easier separ ation of small starch granules and gluten (7,9). Together with pectinases, xylan-degrading enzymes can be used to dissolve of precipitates infruitjuices (Pokomy, M., K R K A Pharmaceuticals, Yugoslavia, personal communication, 1989). Pure xylanases can be useful in basic research. They find application in analytical procedures designed to quantify specific xylan constituents (10) and to study xylan structure. They can be used for preparation of defined xylooligosaccharides, either by hydrolysis of xylan (11-14) or by transglycosylation at high substrate concentrations (15,16). These products may serve as assay substrates and model compounds to study the mechanism of action of xylanolytic enzymes. Finally, xylanolytic enzymes play an important role in complex enzyme preparations used for the release of plant protoplasts. Strategies for Xylanolytic Systems Free of Cellulases Most microorganisms grown under natural conditions produce both cellulases and xy lanases. Biochemistry, microbiology, and molecular biology offer several approaches to obtain xylanase preparations largely or completelyfreeof cellulases (17). Elimination of Cellulases from Xylanases. Classical methods of protein frac tionation can be used for to separate cellulases and xylanases on a large scale only when they differ considerably in molecular weight or isoelectric point. The Tricho derma harzianum enzymes were separated by ultrafiltration because the xylanase was smaller and passed through the membrane into the ultrafiltrate (18). Fractional precip itation with organic solvents is another possibility (1). Cellulases can also be eliminatedfroma mixture with xylanases by selective ther mal inactivation. Cellulases are more thermolabile than xylanases in the cellulolytic systems of the fungus Y-94 (79), T. harzianum (20), and Thermoascus aurantiacus (77), but not in the Trichoderma reesei system (Biely, P. and Vrsanska, M., Slovak Academy of Sciences, Bratislava, unpublished results). Since cellulase thermal inact ivation causes a significant loss of xylanase also, a more convenient way to eliminate cellulase activity is by selective chemical or biological inhibition or inactivation. There appear, however, to be no reports on the existence of natural inhibitors that would be specific for cellulases. Such inhibitors of amylases and pectinases are known to occur in plants (27). Selective inhibition of cellulases by H g in a mixture of cellulases and xylanases of Sporotrichum dimorphosporum used in a laboratory experiments (22) cannot be considered for industrial application for obvious reasons. Specific active-site directed inactivation of cellulases can be achieved using 4,5epoxypentyl β-D-glycosides of cellooligosaccharides, the cellobioside being die most efficient in the inactivating the cellulases (23,24). The derivatizing agents appear to esterify the carboxylate groups of acidic amino acids. The specificity of the reaction was documented by the fact that the control compound 1,2-epoxyhexane did not affect the activity of Schizophyllum commune endo-(1^4)-p-glucanase (24). 2+

Non-Cellulolytic Xylanolytic Microorganisms. Despite the fact that xylan never occurs in nature in the absence of cellulose, there are microorganisms that pro duce only xylanolytic systems. One may speculate that such microorganisms aie sym-


410

ENZYMES IN BIOMASS CONVERSION

biotic with cellulolytic ones. Since cellulase production has been examined in only a minority of xylanolytic microbes, in this section only those xylanolytic strains that are unequivocally cellulase-negative will be mentioned. Xylanolytic strains that do not produce cellulases, as well as xylanases that do not attack cellulose, can be found among yeasts and yeast-like microorganisms (Table I).


Table I. Xylanolytic Yeasts Genus or species

Note

Reference

Aureobasidium pullulons A.pullulans Y-2311-1 Candida sp. Candida shehatae Cryptococcus Pichia stipitis Trichosporon cutaneum

a

25,26 26 27 27 25-27 27 25,28

EG-positive Xylanase hyperproducer

^G-positive

a

Endo-(l->4)-p-glucanase positive.

However, some of the species give a positive test for endo-(l-»4)-p-glucanase activity although they do not grow on cellulose or its soluble derivatives (26-28). It should be noted that the pathogenic yeast Cryptococcus neoformans does not belong to the xylanase-positive family of the Cryptococcus strains (Biely, P., unpublished results). Unfortunately, xylanase production by yeasts is generally low compared to that of fil amentous fungi. Exceptions are color variants of Aureobasidium pullulans Y-2311, which hyperproduce extracellular xylanase (26). Other non-cellulolytic xylanase producers are Butyrivfbriofibrisolvens(29) and a thermotolerant Streptomyces T strain (30). 7

Cellulase-Negative Xylanase-Positive Mutants. There are two reports con cerning the selection of such mutantsfromfilamentous fungi, one on Polyporus adustus (37) and the other on Trichoderma reesei (Durand, H. et al, Société CAYLA, Toulouse, France, unpublished results). An analysis of the eliminated cellulase genes has not been done, so it is not known if the mutants negative in endo-(I-»4)-p-glucanase were deficient also in cellobiohydrolases. The production of cellulase-negative xylanase-positive mutants is much easier from prokaryotic microorganisms that produce less complex enzyme systems and do not have such complicated genetic material. An efficient cellulase-negative xylanaseproducing strain of Streptomyces lividans was obtained by nitrosoguanidine mutagen esis (32). A double cellulase- and xylanase-negative mutant has also been isolated from the same strain (33). The double mutant was transformed to a xylanase-positive one by returning the xylanase gene from the parent 5. lividans strain. The newly con structed transformant gave a considerable overproductton of inducible xylanase (34). Mutants of Polyporus adustus (57), T. viride (35,36), and T. reesei (Durand, H. et α7., unpublished results) that produced neither cellulases nor xylanases have been reported. With the P. adustus mutant it was shown that the pleiotropic mutation was not due to a deletion of cellulase and xylanase genes, but rather to a deficiency of a single regulatory gene that governs the induction of both cellulase and xylanase (37). A similar interpretation was advanced in the case of a T. viride mutant lacking the abil ity to hydrolyze soluble and crystalline cellulose and xylan (36). A defect in a general ability to secrete proteins could be an alternative m explain the phenotypes. Whether the cellulase- and xylanase-negative mutants of filamentous fungi become candidates


31.

BIELY

411


for the introduction of xylanase genes will depend on their ability to harbor and express them. In this context, the efficient host-vector system for genetic modification of T. reesei developed by Penttilâ et al (37) should be mentioned.


Cloning of Xylanase Genes. Recombinant DNA techniques offer great oppor tunities for obtaining microbial producers of cellulase-free xylanases. The strategy is simply to clone a xylanase gene in a cellulase-negative host. Cloning techniques also enable the multiplication of the expression of genes already present. The production of xylanase in Bacillus subtilis was enhanced several times using a plasmid vector carry ing the Bacillus pumilus gene (38). The literature contains numerous examples of cloning xylanase genes with bacterial gene donors and acceptors (Table Π). In most cases strains of Escherichia Table Π. Cloning of Xylanase Genes Gene donor Bacilli Bacillus pumilus B. subtilis B. pumilus (a) B. subtilis B. polymyxa B. polymyxa Bacillus C-125 (alkalophil.) Bacillus C-125 (alkalophil.) B. circulans B. subtilis (b)

Enzyme localization in the host and other notes intracellular intracellular intracellular secreted and periplasmic cell-bound periplasmic extracellular extracellular (secretory vector) intracellular intracellular

Ref.

39 40 38 41 42 43 44 45 46 47

Thermophilic bacteria Aeromonas intracellular 48 Aeromonas secreted 49 Bacteroides succinogenes intracellular (high expression) 50 Clostridium acetobutylicum intracellular (high expression) 51 Clostridium thermocellum xylanase Ζ active on 4-methylumbelliferyl 52 β-D-cellobioside Clostridium thermocellum three xylanase genes 53 Caldocellwn saccharolyticwn intracellular 54 Other strains Pseudomonas fluorescens periplasmic, active on 4-methylumbelliferyl β-D-cellobioside Pseudomonas fluorescens (c) cell-bound Ruminococcus albus intracellular, non-specific Cryptococcus albidus intracellular (eukaryotic donor)

55 55 56 57

Recipients of xylanase genes other than standard E. coli: (a) B. subtilis; (b) "leaky" mutant of E. coli; (c) Pseudomonas putida. coli were used as recipients. In xylanase-positive transformants the products of the expressed genes were only rarely secreted out of the cells, and in a majority of cases they remained localized either intracellularly or in the periplasmic space (Table Π). The problems with enzyme secretionfrombacterial hosts can be overcome by using "leaky"



412


mutants of E. coli, which lyse spontaneously at elevated temperatures, as the hosts (47). Secretion of the expressed gene products can occasionally be achieved by more complicated cloning strategies, which have to be developed for each particular protein. It happens frequently that even when the gene cloned in E. coli is provided with the segment coding for the secretory signal peptide, the expressed gene product stays im prisoned in the periplasmic space. However, there are ways to achieve the extracellular production of foreign proteins by E. coli. One possibility is the fusion of the foreign proteins with some outer membrane proteins (58) or the use of the export system of colicins and hemolysins (59). These approaches have not yet been applied in cloning of xylanase genes. Hamamoto and Horikoshi (45) achieved the secretion of an alkal ine xylanase in E. coli by constructing a special secretion vector. Even this vector did not work with some other proteins. Special attention has been paid by several groups to cloning xylanase genes from thermophilic microorganisms as a source of thermostable xylanases. Cloning of such genes in mesophilic recepients offers a convenient way to purify xylanases simply by a heat denaturation of the more heat-labile proteins of the host (54). Applications are limited to those enzymes that possess thermostability considerably higher than the maj ority of the host cell proteins. Selective Production of Xylanases by Cellulolytic Microorganisms. Until recently there was little information on common or separate genetic control of cellulase and xylanase synthesis in microorganisms (60). Studies on this subject were complic ated by the fact that numerous microbial cellulases and xylanases are non-specific with respect to cellulose and xylan as substrates. As could be expected from a comparison of both polysaccharide structures, non-specificity is more frequently observed with cel lulases, because their substrate binding sites can easily accommodate substrate using an unsubstituted |Hl->4)-linked chain of D-xylopyranosyl units. Recent experimental evidence suggests that production of cellulases and xylanases is under separate regulatory control in several filamentous fungi. Selective production of xylanase can be achieved in Trichoderma and Aspergillus species during growth in media containing xylan as the only carbon source (61-67). On cellulose the strains produce both cellulases and xylanases. The reason for this may be that cellulose is al ways contaminated by xylan remnants. However, an exception is bacterial cellulose that proved to be a poor growth support for fungi (61). The degree of selectivity of formation of xylanases on xylan in T. reesei QM 9414 is dependent on the nitrogen/ carbon ratio in the medium (61,62). The mechanisms that govern the formation of extracellular enzymes with respect to the carbon source present in the medium are in fluenced by the availability of precursors for protein synthesis. A shortage of such precursors causes a more strict separate regulation of the synthesis of cellulases and xylanases by available carbon sources. Therefore, the strategy for producing xylano lytic systems free of cellulases in some fungi might be to grow the cells on xylan not contaminated by cellulose, and under a lower nitrogen/carbon ratio in the medium. However, this strategy cannot be applied to all fungi. For instance, xylanase produc tion in S. commune could not be separated from cellulase synthesis (62,68). Unfortunately, pure xylan is an expensive carbon source for commercial-scale xylanase production. Therefore, several groups have tried to develop xylanase produc tion on cheaper xylan-rich materials. The best candidates for the purpose appear to be water-soluble hemicellulose from steam-treated wood (63,69) and residues of annual plants like wheat bran (70). Low-Molecular Weight Xylanase Inducers. The response of cellulolytic fungi to low-molecular weight fragments of xylan and cellulose confirmed the separate regulatory control of the formation of xylanases and cellulases. Xylobiose [Xylp-β(l->4)-Xylp] was a specific inducer of xylanases in T. reesei (61) and Aspergillus terreus (67). Sophorose and other glucobioses selectively induced the synthesis of



31. BIELY


413

cellulases (61,67). The non-specific endo-(l->4)-p-glucanase (EG I) of T. reesei that attacks both cellulose and xylan is inducible by sophorose and not by xylobiose, sup porting the conclusion that the enzyme is a component of the cellulolytic system of the fungus (61). Xylan fragments induced xylanase also in non-cellulolytic microorganisms like Streptomyces sp. (71) and yeasts of the genus Cryptococcus and Trichosporon (72-74). In these strains xylanase could be efficiently induced also by methyl β-Dxylopyranoside, which is extremely slowly metabolized in the cells (72-74). The gly coside accelerated xylanase production in hyperproducing color variants of A. pullulans (75) and in several strains of Aspergillus (70). Low cost and easy preparation of methyl β-D-xylopyranoside favors its use for large-scale xylanase production. Xylanolytic systems of yeasts and fungi can also be induced by positional iso mers of xylobiose. Induction with Χν1/λ-β-(1-»2)-Χν1/? is analogous to the sophorose induction of cellulase in filamentous fungi (76). Χν1ρ-β-(1->2)-Χν1ρ and Xylp-β(l-»3)-Xyl/? induced xylanase in C. albidus (77), Trichosporon cutaneum (73), A. pullulans (78) and A. terreus (Hrmova, M . et al., Slovak Academy of Sciences, Bratislava, submitted for publication, 1990). In C. albidus the positional isomers be have differently than does xylobiose (77), in that the response of the cells to them was slower but the enzyme yields were higher than in the presence of xylobiose. This inicated that isomeric xylobioses were not direct inducers. In agreement with this idea, both Χν1/?-β-(1->2)-Χν1/? and Χν1ρ-β-(1->3)-Χν1/? were transformed to Xyl/7-β(l->4)-Xylp, the natural inducer (79). The variety of control mechanisms of xylanase synthesis is demonstrated by ex amples of the synthesis of xylanase induced by xylose (38,74,75). To a list of lowmolecular weight xylanase inducers one can add 4-thioxylobiose (80,81) and 4-0-β-ϋxylopyranosyl-L-arabinopyranose (73,77). Future Directions No doubt the cost of xylanolytic enzymes will be one of the factors determining their application in the pulp and paper industry as well as in other areas. Economically feas ible xylanase production can be achieved in paper mills employing xylanase-positive transformants of common industrially used microorganisms that are capable of utilizing inexpensive carbon sources originating there. A substantial improvement in the pro duction of xylanolytic systems can be expected from mutants of non-cellulolytic micro organisms that are resistant to catabolic repression. Such mutants usually exhibit hyperproduction of extracellular enzymes. More investigation is needed to establish requirements for the properties of xylan olytic enzymes used for upgrading pulp. A question is whether the applied enzyme preparations should be complex xylanolytic systems or just a single endo-(l->4)^xylanase. The presence of β-xylosidase may not be required because the primary goal will not be xylose production. Other properties of xylanases may be of interest in con nection with their application in the pulp-bleaching sequence. These include their mol ecular weights, thermostabilities, operational stabilities in alkaline or acidic media, and sizes of their substrate binding sites. Smaller xylanases may penetrate more easily into the pulp structure. Xylanases with smaller binding sites, i.e. smaller number of subsites, will be more efficient in the depolymerization of xylans substituted to a higher degree. Further progress can be expected in the area of selective inhibition and inactivat ion of cellulases undesirable in xylanase preparations. There is a possibility of finding natural selective cellulase inhibitors or developing highly reactive derivatives of cello biose and celtodextrins that inactivate cellulolytic enzymes. Finally, attention should also be devoted to the elaboration of simple and reliable assays of xylanolytic enzymes that provide information on their efficiency in the applic ation process.


414



Literature Cited 1. Paice, M . G.; Jurasek, L. J. Wood Chem. Technol.1984, 4, 187-98. 2. Viikari, L.: Rauna, M.; Kantelinen, Α.; Sundquist, J.; Linko, M . In Proc. 3rd Int. Conf. Biotechnology in the Pulp and Paper Industry; Eriksson, K.-E.; Ander, P., Eds.; STFI, Stockholm, 1986; pp 67-9. 3. Viikari, L.; Rauna, M.; Kantelinen, Α.; Linko, M.; Sundquist, J. In Proc. 4th Int. Conf. Wood and Pulping Chemistry, Paris, 1987, Vol. I; pp 151-4. 4. Mora, F.; Comtat, J.; Barnoud, F.; Pla, F.; Noe, P. J. Wood Sci. Technol. 1986, 6, 147-65. 5. Noe, P.; Chevalier, J.; Mora, F.; Comtat, J. J. Wood Sci. Technol. 1986, 6, 167-84. 6. Van Sumere, C. F. Proc. Danish Technical Days in Prague, 1986; pp. 1-16. 7. McCleary, Β. V. Int. J. Biol. Macromol. 1986, 8, 349-54. 8. Shibuya, N.; Iwasaki, T. Nippon Shokuhin Kogyo Gakkaishi 1984, 31, 65660. 9. Wieg, A. J. Starch/Stärke 1984, 36, 135-40. 10. Puls, J.; Poutanen, K. Proc. 4th Int. Conf. Wood and Pulping Chemistry, Paris, 1987, Vol. I; pp. 211-4. 11. Timell, T. G. Svensk Pappersindn. 1962, 65, 435-47. 12. Kusakabe, I.; Yasui, T.; Kobayashi, T. Agr. Biol. Chem. 1975, 39, 1355-62. 13. Cavagna, F.; Deger, H,; Puls, J. Carbohydr. Res. 1984, 129, 1-8. 14. Kusakabe, I.; Ohgushi, S.; Yasui, T.; Kobayashi, T. Agr. Biol. Chem. 1983, 47, 2713-23. 15. Kratky, Z.; Biely, P.; Vrsanska, M . Carbohydr. Res. 1981, 93, 300-303. 16. Biely, P.; Vrsanska, M . Eur. J. Biochem. 1983, 129, 645-51. 17. Senior, D. J.; Mayers, P. R.; Saddler, J. N. In Plant Cell Wall Polymers: Biogenesis and Biodegradation; Lewis, N. G.; Paice, M. G., Eds.; Am. Chem. Soc. Symp. Ser. 399, Washington, D. C., 1989; pp 630-40. 18. Tan, L. U. L.; Yu, E. K. C.; Luis-Seize, G. W.; Saddler, J. N. Biotechnol. Bioeng. 1987, 30, 96-100. 19. Mitsuishi, Y.; Yamanobe, T.; Yagashiwa, M.; Takasaki, T. Agr. Biol. Chem. 1987, 51, 3207-13. 20. Todorovic, R.; Matavujl, M.; Grujic, S.; Petrovic, J. Mikrobiologia 1986, 23, 33-8. 21. Albersheim, P.; Anderson, A. J. Proc. Nat. Acad. Sci. U.S.A. 1971, 68, 1815-9. 22. Barnoud, F.; Comtat, J.; Joseleau, J. P.; Mora, F.; Ruel, K. Proc. 3rd Int. Conf. Biotechnology in the Pulp and Paper Industry; Eriksson, K.-E.; Ander, P., Eds.; STFI, Stockholm, 1986; pp 70-2. 23. Legler, G.; Bause, E. Carbohydr. Res. 1973, 28, 45-52. 24. Clarke, A. J.; Strating, H. Carbohydr. Res. 1989, 188, 245-50. 25. Biely, P.; Kratky, Z.; Kockova-Kratochvilova, Α.; Bauer, S. Folia Microbiol. 1978, 23, 366-71. 26. Leathers, T. D.; Kurtzman, C. P.; Detroy, R. W. Biotechnol. Bioeng. Symp., 1984, 14, 225-40. 27. Lee, H.; Biely, P.; Latta, R. K.; Barbosa, M. F. S.; Schneider, H. Appl. En viron. Microbiol. 1986, 52, 320-4. 28. Stevens, B. J. H.; Payne, J. J. Gen. Microbiol. 1977, 100, 381-93. 29. Van Der Toorn, J. J. T. K.; Van Gylswyk, N . O. J. Gen. Microbiol. 1985, 131, 2601-7. 30. Keskar, S. S.; Srinivasan, M . C.; Deshpande, V. V. Biochem. J. 1989, 261, 49-55. 31. Eriksson, K.-E.; Goodell, E. W. Can. J. Microbiol. 1974, 20, 371-8. 32. Mondou, F.; Shareck, F.; Morosoli, F.; Kluepfel, D. Gene 1986, 49, 323-9.


31. BIELY


415


33. Morosoli, R.; Bertrand, J.-L.; Mondou, F.; Shareck, F.; Kluepfel, D. Bio chem. J. 1986, 239, 587-92. 34. Bertrand, J.-L.; Morosoli, R.; Shareck, F.; Kluepfel, D. Biotechnol. Bioeng. 1989, 33, 791-4. 35. Mandels, M.; Weber, J.; Parizek, R. Appl. Microbiol. 1971, 21, 152-4. 36. Nevalainen, K. M. H.; Palva, Ε. T. Appl. Environ. Microbiol. 1978, 35, 1116. 37. Penttilä, M.; Nevalainen, H.; Ratto, R.; Salminen, E.; Knowles, J. Gene 1987, 61, 155-64. 38. Panbangred, W.; Fukusaki, E.; Epifanio, E. C.; Shinmyo, Α.; Okada, H. Appl. Microbiol. Biotechnol. 1985, 22, 259-64. 39. Panbangred, W.; Kondo, T.; Negoro, S.; Shinmyo, Α.; Okada, H. J. Mol. Gen. Genet. 1983, 192 , 334-41. 40. Bernier, R. Jr.; Driguez, H.; Desrochers, M. Gene 1983, 26, 59-65. 41. Paice, M. G.; Bernier, R., Jr.; Jurasek, L. Biotechnol. Bioeng. 1988, 32, 235-9. 42. Sandhu, J. S.; Kennedy, J. F. Enzyme Microb. Technol. 1984, 6, 271-4. 43. Yang, R. C. Α.; MacKenzie, C. R.; Bilous, D.; Seligi, V.; Narang, S. A. Appl. Environ. Microbiol. 1988, 54, 1023-9. 44. Honda, H.; Kudo, T.; Horikoshi, K. J. Bacteriol. 1985, 161, 784-5. 45. Hamamoto, T.; Horikoshi, K. Agr. Biol. Chem. 1987, 51, 3133-5. 46. Yang, R. C.; MacKenzie, C. R.; Bilous, D.; Narang, S. A. Appl. Environ. Microbiol. 1989, 55, 1192-5. 47. Pechan, P.; Barak, I.; Jucovic, M.; Biely, P.; Timko, J. Biológia (Bratislava) 1989, 44, 1137-45. 48. Kudo, T.; Ohnishi, Α.; Horikoshi, K. J. Gen. Microbiol. 1985, 131, 282530. 49. Kato, C.; Kobayashi, T.; Kudo, T.; Horikoshi, K. FEMS Microbiol. Lett. 1986, 36, 31-4. 50. Sipat, Α.; Taylor, Κ. Α.; Lo, R. Y. C.; Forsberg, C. W.; Krell, P. J. Appl. En viron. Microbiol. 1987, 53, 477-81. 51. Zappe, H.; Jones, D. T.; Woods, D. R. Appl. Microbiol. Biotechnol. 1987, 27, 57-63. 52. Grepinet, O.; Chebron, M.-C.; Beguin, P. J. Bacteriol. 1988, 170, 4582-8. 53. MacKenzie, C. R.; Yang, R. C. Α.; Patel, G. P.; Bilous, D.; Narang, S. A. Arch. Microbiol. 1989, 152, 377-81. 54. Patchett, M . L.; Neal, T. L., Schofield, L. R.; Strange, R. C.; Daniel, R. M.; Morgan, H. W. Enzyme Microb. Technol. 1989, 11, 113-5. 55. Gilbert, H. J.; Sullivan, D. Α.; Jenkins, G.; Kellett, L. E.; Minton, N. P.; Hall, J. J. Gen. Microbiol. 1988, 134, 3239-47. 56. Romaniec, M. P.; Davidson, K.; White, Β. Α.; Hazlewood, G. P. Lett. Appl. Microbiol. 1989, 9, 101-4. 57. Morosoli, R.; Durand, S. FEMS Microbiol. Lett. 1988, 51, 217-24. 58. Nagahari, K.; Kanaya, S.; Munakata, M.; Aoyagi, K. ; Mizushima, S. EMBO J. 1985, 4, 3589-92. 59. Kobayashi, T.; Kato, C.; Kudo, T.; Horikoshi, K. J. Bacteriol. 1986, 166, 728-32. 60. Dekker, R. F. H.; Richards, G. N. Adv. Carbohydr. Chem. Biochem. 1976, 32, 277-352. 61. Hrmova, M.; Biely, P.; Vrsanska, M. Arch. Microbiol. 1986, 144, 307-11. 62. Biely, P.; MacKenzie, C. R.; Schneider, H. Can. J. Microbiol. 1988, 34, 767-72. 63. Senior, D. J.; Mayers, P. R.; Saddler, J. N. Appl. Microbiol. Biotechnol. 1989, 32, 137-42. 64. Royer, J. C.; Nakas, J. P. Enzyme Microb. Technol. 1989, 11, 405-10.



416


65. Eriksson, K.-E.; Rzedowski, W. Arch. Biochem. Biophys. 1969, 129, 683-8. 66. Stewart, J. C.; Lester, Α.; Milburn, B.; Parry, J. B. Biotechnol. Lett. 1983, 5, 543-8. 67. Hrmova, M.; Biely, P.; Vrsanska, M . Enzyme Microb. Technol. 1989, 11, 610-16. 68. Steiner, W., Lafferty, R. M.; Gomes, I.; Esterbauer, H. Biotechnol. Bioeng. 1987, 30, 169-78. 69. Schmidt, O.; Puls, J.; Sinner, M.; Dietrichs, H. H. Holzforschung 1979, 33, 192-6. 70. Bailey, M.; Poutanen, K. Appl. Microbiol. Biotechnol. 1989, 30, 5-10. 71. Nakanishi, K.; Yasui, T. Agr. Biol. Chem. 1980, 44, 2729-30. 72. Biely, P.; Krátky, Z.; Vrsanska, M.; Urmanicova, D. Eur. J. Biochem. 1980, 108, 323-9. 73. Hrmova, M.; Biely, P.; Vrsanska, M.; Petrakova, E. Arch. Microbiol. 1984, 138, 371-6. 74. Yasui, T.; Nguyen, B. T.; Nakanishi, K. J. Ferment. Technol. 1984, 62, 353-9. 75. Leathers, T. D.; Detroy, R. W.; Bothast, R. J. Biotechnol. Lett. 1986, 8, 867-72. 76. Mandels, M.; Parrish, F. W.; Reese, E. T. J. Bacteriol. 1962, 83, 400-8. 77. Biely, P.; Petrakova, E. J. Bacteriol. 1984, 160, 408-12. 78. Pou-Llinas, J.; Driguez, H. Appl. Microbiol. Biotechnol. 1987, 27, 134-8. 79. Biely, P. Petrakova, E. FEBS Lett. 1984, 178, 323-6. 80. Defaye, J.; Driguez, H.; John, M.; Schmidt, J.; Ohleyer, E. Carbohydr. Res. 1985, 139, 123-32. 81. Biely, P.; Defaye, J. Abstracts FEMS Symp. Biochemistry and Genetics of Cellulose Degradation, Paris, 1987; p 98. RECEIVED September 26,

1990


Enzymes in Biomass Conversion - ACS Publications - American

Recommend Documents