Production of Bioethanol from Spoilage Date Fruits by New Osmotolerant Yeasts

Abstract

This research aimed at the production of bioethanol from a cheap and renewable resource (spoilage dates) by nonconventional yeasts to reduce total cost of the production. Chemical, physical or biological pretreatment of the spoilage date juice (SDJ) did not affect the availability of fermentable sugars significantly. The isolated osmotolerant yeast strains: Pichia kudriavzevii KKUY-0034, Hanseniaspora opuntiae KKUY-0152 and H. uvarum KKUY-0078, which were genetically identified based on sequences of D1/D2 domain 26S rRNA gene and phylogenetic analysis, were tested for their fermentability of the SDJ. The fermentation conditions were adjusted to induce the maximum production of ethanol. Results showed that the highest quantities of ethanol were obtained when the yeasts were grown on 20% of date juice at 30°C and when the pH was adjusted at 4-6 for 60 h. Addition of either Zn or Mg (0.4 g/L) and NH4H2PO4 (4 g/L) had a good impact on the ethanol productivity by the three species, however, H. uvarum KKUY-0078 was the leader that produced 60 g/L of ethanol. In 7-L fermentor, when the optimum conditions were kept constant, ethanol production reached to 80 g/L after 60 h. The study concludes that SDJ is a promising and costless substrate for production of the bioenergy and using the osomtolerant yeasts is an economic strategy. The partial 26S rRNA gene sequences of P. kudriavzevii KKUY-0034, H. uvarum KKUY-0078 and H. opuntiae KKUY-0152 were deposited in the DDBJ, EMBL, and GenBank database under the accession Nos. JQ690250, JQ690236 and KC110834, respectively.

On the Optimization of Fermentation Conditions for Enhanced Bioethanol Yields from Starchy Biowaste via Yeast Co-Cultures

“…The increase in the ethanol concentration in a 7-L fermenter could be related to various parameters that are affected by the scaling-up of a fermentation process such as the improved agitation and pH control. Indeed, in the 7-L-fermenter agitation was performed via mechanical stirring and not in a rotary shaker as in the flask experiments, resulting in more efficient mixing of the fermentation broth and consequently to better availability of the nutrients to the biocatalysts, leading thus to better productivities and yields [44]. Moreover, better mixing during the fermentation is reported to allow for more effective gas-liquid mass transfer [45] leading thus to better exchange of oxygen and fermentation gases [46] and also for more efficient heat transfer [47], which is expected to ensure optimal distribution of heat throughout the volume of the reactor.…”

Isolation and Identification of the Hanseniaspora opuntiae MK 460485 as an efficient strain for ethanol production

“…Pratt-Marshall et al (2003) and Reddy and Reddy (2006) in separate studies showed that sugar concentrations increasing had a highly inhibiting effect on yeast growth and their capability to ethanol production [32,33]. This reduction is due to production of other compounds than ethanol and also rising of intracellular toxic ethanol concentration [34] which can stop the fermentation process and finally ethanol formation [35]. Several authors have used different Hanseniaspora strains in the fermentation processes.…”