Browsing by Author "Teixeira, Pedro D."
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- Screening of novel yeast inulinases and further application to bioprocessesPublication . Paixão, Susana M.; Teixeira, Pedro D.; Silva, Tiago; Teixeira, A. V.; Alves, LuísInulin is a carbohydrate composed of linear chains of ß-2,1-linked D-fructofuranose molecules terminated by a glucose residue through a sucrose-type linkage at the reducing end. Jerusalem artichoke (JA) is one of the most interesting materials among unconventional and renewable raw materials, with levels of inulin reaching 50–80% of dry matter. Inulin or inulin-rich materials can be actively hydrolyzed by microbial inulinases to produce glucose and fructose syrups that can be used in bioprocesses. In this study, several microbial strains were isolated and their ability to inulinase biosynthesis was evaluated. The novel yeast strain Talf1, identified as Zygosaccharomyces bailii, was the best inulinase producer, attaining 8.67 U/ml of inulinase activity when JA juice was used as the inducer substrate. Z. bailii strain Talf1 and/or its enzymatic crude extract were further applied for bioethanol production and biodesulfurization (BDS) processes, using inulin and JA juice as carbon source. In a consolidated bioprocessing for ethanol production from 200 g/l inulin, Z. bailii strain Talf1 was able to produce 67 g/l of ethanol. This ethanol yield was improved in a simultaneous saccharification and fermentation (SSF) process, with the ethanologenic yeast Saccharomyces cerevisiae CCMI 885 and the Talf1 inulinases, achieving a production of 78 g/l ethanol. However, the highest ethanol yield (~48%) was obtained in a SSF process from JA juice (~130 g/l fermentable sugars), where the S. cerevisiae produced 63 g/l ethanol. Relatively to the dibenzothiophene BDS tests, the Gordonia alkanivorans strain 1B achieved a desulfurization rate of 4.8 µM/h within a SSF process using Talf1 inulinases and JA juice, highlighting the potential of JA as a less expensive alternative carbon source. These results showed the high potential of Z. bailii strain Talf1 inulinases as a versatile tool for bioprocesses using inulin-rich materials.
- Zygosaccharomyces bailii strain talf1 inulinases/invertases towards enhanced bioprocessesPublication . Paixão, Susana M.; Arez, B. F.; Silva, Tiago; Teixeira, Pedro D.; Alves, LuísZygosaccharomyces bailii strain Talf1, a yeast recently isolated in our laboratory, produces a crude enzymatic extract that was determined to have both inulinase/ invertase activities. The properties of these activities were characterized and the crude extract was applied towards bioprocesses. The extracellular crude enzymatic extract presents activity in a range of temperatures from 20 to 60°C and pH from 4.5 to 7. Optimal pH and temperature was 5.5 and 50°C for both activities, with long-term thermostability at 25-30°C and pH 5.5. Maximal activities on crude were obtained when Jerusalem artichoke (JA) was used as inducer, attaining 18 and 156 U/ml of inulinase and invertase activities, respectively. Z. bailii Talf1 was used for bioethanol production through consolidated bioprocessing using JA juice as the only nutrients medium (~130 g/l total hydrolysable sugars), producing 67 g/l of ethanol and attaining the maximum theoretical yield (0.51 g/g hydrolysable sugars). Moreover, the crude enzymatic extract was applied for fossil fuels biodesulfurization. Thus, two renewable agro-materials, sugar beet molasses (SBM) and JA, were exploited as cheaper carbon sources for a cost-effective dibenzothiophene desulfurization process by Gordonia alkanivorans strain 1B through simultaneous saccharification and fermentation (SSF) approach. SSF with invertases/inulinases permitted an increase in 2-hydroxybiphenyl specific production rate of 19.5% from SBM (2.61 to 3.12 µmol g-1DCW h-1) and 64.6% (5.06 to 8.33 µmol g-1DCW h-1) from JA juice in comparison to acidic hydrolysis. These results highlight the potential of Talf1 as a CBP strain towards bioethanol and of its enzymatic crude towards enhanced biodesulfurization.
- Zygosaccharomyces bailii strain talf1 inulinases: a versatile tool for bioprocessesPublication . Paixão, Susana M.; Teixeira, Pedro D.; Silva, Tiago; Teixeira, A. V.; Alves, LuísFructans are one of the most abundant non-structural polysaccharides found in a wide range of plants. Inulin is a polydisperse fructan polymer composed by linear chains of b-2, 1-linked D-fructofuranose molecules terminated by a glucose residue through a sucrose-type linkage at the reducing end. Inulin or inulin-rich materials can be actively hydrolyzed into fermentable sugars (glucose and fructose) using inulinases and then further used within bioprocesses.