Screening of bacteria to produce polyhydroxyalkanoates from xylose |
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Authors: | Mateus Schreiner Garcez Lopes Rafael Costa Santos Rocha Sandra Patricia Zanotto José Gregório Cabrera Gomez Luiziana Ferreira da Silva |
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Institution: | 1.Departamento de Microbiologia,Universidade de S?o Paulo,S?o Paulo,Brazil;2.Mestrado em Biotecnologia,Universidade do Estado do Amazonas,Manaus,Brazil |
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Abstract: | Although xylose is a major constituent of lignocellulosic feedstock and the second most abundant sugar in nature, only 22%
of 3,152 screened bacterial isolates showed significant growth in xylose in 24 h. Of those 684, only 24% accumulated polyhydroxyalkanoates
after 72 h. A mangrove isolate, identified as Bacillus sp. MA3.3, yielded the best results in literature thus far for Gram-positive strains in experiments with glucose and xylose
as the sole carbon source. When glucose or xylose were supplied, poly-3-hydroxybutyrate (PHB) contents of cell dry weight
were, respectively, 62 and 64%, PHB yield 0.25 and 0.24 g g−1 and PHB productivity (PPHB) 0.10 and 0.06 g l−1 h−1. This 40% PPHB difference may be related to the theoretical ATP production per 3-hydroxybutyrate (3HB) monomer calculated as 3 mol mol−1 for xylose, less than half of the ATP/3HB produced from glucose (7 mol mol−1). In PHB production using sugar mixtures, all parameters were strongly reduced due to carbon catabolite repression. PHB production
using Gram-positive strains is particularly interesting for medical applications because these bacteria do not produce lipopolysaccharide
endotoxins which can induce immunogenic reactions. Moreover, the combination of inexpensive substrates and products of more
value may lead to the economical sustainability of industrial PHB production. |
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