RESUMEN
Kraft pulp is a promising feedstock for bioproduction. The efficiency of kraft pulp saccharification was improved by using a cellulase cocktail prepared from genetically engineered Aspergillus oryzae. Application of the cellulase cocktail was demonstrated by simultaneous saccharification and fermentation, using kraft pulp and non-cellulolytic yeast. Such application would make possible to do an efficient production of other chemicals from kraft pulp.
Asunto(s)
Aspergillus oryzae/genética , Aspergillus oryzae/metabolismo , Celulasa/metabolismo , Celulosa/química , Ingeniería Genética , Fermentación , Hidrólisis , Plásmidos/genética , Madera/químicaRESUMEN
BACKGROUND: Kojic acid (5-Hydroxy-2-(hydroxymethyl)-4-pyrone) is one of the major secondary metabolites in Aspergillus oryzae. It is widely used in food, pharmaceuticals, and cosmetics. The production cost, however, is too high for its use in many applications. Thus, an efficient and cost-effective kojic acid production process would be valuable. However, little is known about the complete set of genes for kojic acid production. Currently, kojic acid is produced from glucose. The efficient production of kojic acid using cellulose as an inexpensive substrate would help establish cost-effective kojic acid production. RESULTS: A kojic acid transcription factor gene over-expressing the A. oryzae strain was constructed. Three genes related to kojic acid production in this strain were transcribed in higher amounts than those found in the wild-type strain. This strain produced 26.4 g/L kojic acid from 80 g/L glucose. Furthermore, this strain was transformed with plasmid harboring 3 cellulase genes. The resultant A. oryzae strain successfully produced 0.18 g/L of kojic acid in 6 days of fermentation from the phosphoric acid swollen cellulose. CONCLUSIONS: Kojic acid was produced directly from cellulose material using genetically engineered A. oryzae. Because A. oryzae has efficient protein secretion ability and secondary metabolite productivity, an A. oryzae-based cell factory could be a platform for the production of various kinds of bio-based chemicals.
Asunto(s)
Aspergillus oryzae/genética , Aspergillus oryzae/metabolismo , Celulosa/metabolismo , Pironas/metabolismo , Aspergillus oryzae/crecimiento & desarrollo , Técnicas de Cultivo Celular por Lotes , Celulasa/genética , Celulasa/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Glucosa/metabolismo , Plásmidos/genética , Plásmidos/metabolismo , Pironas/químicaRESUMEN
Lactic acid is a commodity chemical that can be produced biologically. Lactic acid-producing Aspergillus oryzae strains were constructed by genetic engineering. The A. oryzae LDH strain with the bovine L-lactate dehydrogenase gene produced 38 g/L of lactate from 100g/L of glucose. Disruption of the wild-type lactate dehydrogenase gene in A. oryzae LDH improved lactate production. The resulting strain A. oryzae LDHΔ871 produced 49 g/L of lactate from 100g/L of glucose. Because A. oryzae strains innately secrete amylases, A. oryzae LDHΔ871 produced approximately 30 g/L of lactate from various starches, dextrin, or maltose (all at 100 g/L). To our knowledge, this is the first report describing the simultaneous saccharification and fermentation of lactate from starch using a pure culture of transgenic A. oryzae. Our results indicate that A. oryzae could be a promising host for the bioproduction of useful compounds such as lactic acid.