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Applied and Environmental Microbiology, March 1999, p. 893-897, Vol. 65, No. 3
Department of Chemical Engineering, North
Carolina State University, Raleigh, North Carolina 27695
Received 31 August 1998/Accepted 1 December 1998
Utilization of a range of carbohydrates for growth by the
hyperthermophile Pyrococcus furiosus was investigated by
examining the spectrum of glycosyl hydrolases produced by this
microorganism and the thermal labilities of various saccharides.
Previously, P. furiosus had been found to grow in batch
cultures on several
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Copyright © 1999, American Society for Microbiology. All rights reserved.
Relationship between Glycosyl Hydrolase Inventory
and Growth Physiology of the Hyperthermophile Pyrococcus
furiosus on Carbohydrate-Based Media
and
-linked carbohydrates and cellobiose but not on
glucose or other
-linked sugars. Although P. furiosus
was not able to grow on any nonglucan carbohydrate or any form of
cellulose in this study (growth on oat spelt arabinoxylan was
attributed to glucan contamination of this substrate), significant
growth at 98°C occurred on
-1,3- and
-1,3-
-1,4-linked
glucans. Oligosaccharides generated by digestion with a recombinant
laminarinase derived from P. furiosus were the compounds
that were most effective in stimulating growth of the microorganism. In
several cases, periodic addition of
-glucan substrates to fed-batch
cultures limited adverse thermochemical modifications of the
carbohydrates (i.e., Maillard reactions and caramelization) and led to
significant increases (as much as two- to threefold) in the cell
yields. While glucose had only a marginally positive effect on growth
in batch culture, the final cell densities nearly tripled when glucose
was added by the fed-batch procedure. Nonenzymatic browning reactions
were found to be significant at 98°C for saccharides with degrees of
polymerization (DP) ranging from 1 to 6; glucose was the most labile
compound on a mass basis and the least labile compound on a molar
basis. This suggests that for DP of 2 or greater protection of the
nonreducing monosaccharide component may be a factor in substrate
availability. For P. furiosus, carbohydrate utilization
patterns were found to reflect the distribution of the glycosyl
hydrolases which are known to be produced by this microorganism.
*
Corresponding author. Mailing address: Department of
Chemical Engineering, North Carolina State University, Box 7905, Raleigh, NC 27695-7905. Phone: (919) 515-6396. Fax: (919) 515-3465. E-mail: rmkelly{at}eos.ncsu.edu.
Present address: Novartis Agribusiness Research, Inc., Research
Triangle Park, NC 27709.
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