Inhibition of Pichia stipitis fermentation of hydrolysates from olive tree cuttings
The ethanolic fermentation of liquid fractions (hydrolysates) issued from dilute acid pre-treatment of olive tree biomass by Pichia stipitis is reported for the first time. On the one side, P. stipitis has been reported as the most promising naturally occurring C5 fermenting microorganism; on the other side, olive tree biomass is a renewable, low cost, and lacking of alternatives agricultural residue especially abundant in Mediterranean countries. The study was performed in two steps. First, the fermentation performance of P. stipitis was evaluated on a fermentation medium also containing the main inhibitors found in these hydrolysates (acetic acid, formic acid, and furfural), as well as glucose and xylose as carbon sources. The effect of inhibitors, individually or in a mixture, on kinetic and yield parameters was calculated. In a second step, hydrolysates obtained from 1% (w/w) sulfuric acid pre-treatment of olive tree biomass at 190°C for 10 min were used as a real fermentation medium with the same microorganism. Due to inhibition, effective fermentation required dilution of the hydrolysate and either overliming or activated charcoal treatment. Results show that ethanol yields obtained from hydrolysates, ranging from 0.35 to 0.42 g/g, are similar to those from synthetic medium, although the process proceeds at lower rates. Inhibiting compounds affect the fermentation performance in a synergistic way. Furfural is rapidly assimilated by the yeast; acetic acid and formic acid concentrations decrease slowly during the process. Activated charcoal or overliming detoxification improve the fermentability of diluted hydrolysates.
KeywordsDetoxification Ethanol Fermentation inhibition Olive tree biomass Pichia stipitis
This work was partially financed by Agencia Española de Cooperación Internacional para el Desarrollo (AECID) under Project ref. D/9619/07, Ministerio de Educación y Ciencia (Project ENE2005-08822) and FEDER funds. Financial support from Azucareras Reunidas de Jaén, S. A. is also gratefully acknowledged.
- Delgenes JP, Moletta R, Navarro JM (1996) Effects of lignocellulose degradation products on ethanol fermentations of glucose and xylose by Saccharomyces cerevisiae, Zymomonas mobilis, Pichia stipitis, and Candida shehatae. Enzyme Microb Technol 19:220–225. doi: 10.1016/0141-0229(95)00237-5 CrossRefGoogle Scholar
- Hallborn J, Gorwa MF, Meinander N, Penttilä M, Keränen S, Hahn-Hägerdal B (1994) The influence of cosubstrate and aeration on xylitol formation by recombinant Saccharomyces cerevisiae expressing the XYL1 gene. Appl Microbiol Biotechnol 42:326–333Google Scholar
- Oliva JM, Sáez F, Ballesteros I, González A, Negro MJ, Manzanares P, Ballesteros M (2003) Effect of lignocellulosic degradation compounds from steam explosion pretreatment on ethanol fermentation by thermotolerant yeast Kluyveromyces marxianus. Appl Biochem Biotechnol 105–108:141–153. doi: 10.1385/ABAB:105:1-3:141 CrossRefGoogle Scholar
- Palmqvist E, Grage H, Meinander NQ (1999a) Main and interaction effects of acetic acid, furfural, and p-hidroxybenzoic acid on growth and ethanol productivity of yeast. Biotechnol Bioeng 63:46–55. doi: 10.1002/(SICI)1097-0290(19990405)63:1<;46::AID-BIT5>;3.0.CO;2-J CrossRefGoogle Scholar
- Palmqvist E, Almeida JS, Hahn-Hägerdal B (1999b) Influence of furfural on anaerobic glycolytic kinetics of Saccharomyces cerevisiae in batch culture. Biotechnol Bioeng 62:447–454. doi: 10.1002/(SICI)1097-0290(19990220)62:4<;447::AID-BIT7>;3.0.CO;2-0 CrossRefGoogle Scholar
- Persson J, Andersson J, Gorton L, Larsson S, Nilvebrant N, Jönsson L (2002) Effect of different forms of alkali treatment on specific fermentation inhibitors and on the fermentability of lignocellulose hydrolysates for production of fuel ethanol. J Agric Food Chem 50:5318–5325. doi: 10.1021/jf025565o CrossRefGoogle Scholar
- Ranatunga TD, Jervis J, Helm RF, McMillan JD, Wooley RJ (2000) The effect of overliming on the toxicity of dilute acid pretreated lignocellulosics: the role of inorganics, uronic acids and ether-soluble organics. Enzyme Microb Technol 27:240–247. doi: 10.1016/S0141-0229(00)00216-7 CrossRefGoogle Scholar