Evaluation of Second-Generation Biofuels Production from Halophytes by Focusing on Wet-Fractionation of Native Halophyte Salicornia sinus-persica

Abstract

Abu Dhabi exemplifies a coastal desert that is surrounded by seawater from three sides, allowing for cultivation of salt-tolerant crops (halophytes). In this study, the halophytes Salicornia bigelovii (dry) and Salicornia sinus-persica (fresh) were evaluated for their potentials to be used as feedstocks for bioethanol production. The main focus of the study was to utilize the native halophyte Salicornia sinus-perica harvested fresh (green). Salicornia sinus-perica contains about 70% of water. For such green biomass direct fractionation and fermentation is advantageous, since it allows water preservation in the system. Chemical characterization and ethanol production potential of the fractionated Salicornia sinus-perica were examined. The fresh untreated pulp fraction showed sugar content that is comparable to conventional crops; particularly 16.27 ± 1.47 g/100 g dry mass (DM) glucose, 11.57 ± 1.00 g/100 g DM of fructose and xylose combined, 1.79 ± 0.03 g/100g DM galactose and 11.04 ± 1.19 g/100g DM arabinose. In order to optimize sugar recovery and fermentability of the pulp fraction, a pre-treatment study was conducted, showing that ethanol yields obtained are directly proportional to the applied pre-treatment temperature (for temperatures ranging between 120 ˚C and 170 ˚C). Ethanol yields increased by 10 folds for pulp pre-treated at 170 ˚C compared to the pulp treated at 120 ˚C when the residence time was fixed at 10 minutes. Juice fermentation obtained high ethanol yields (~100%), however due to its low sugar content (1.0-1.5 %), production of other value-added chemicals was considered. Juice fermentation showed noticeable production of organic acids, which is probably achieved due to contamination with bacteria. Juice sterilization and acid hydrolysis did not enhance the sugar convertibility of the juice, hence fresh juice utilization is recommended. For future work, Salicornia sinus-persica needs to be evaluated for production of added-value chemicals (proteins and nutraceuticals), which can improve the economy of salicornia-based biorefinery.

Date of Award	May 2014
Original language	American English
Supervisor	Mette H. Thomsen (Supervisor)