Utilization of membrane processes for separation of succinic acid after fermentation of Miscanthus biomass

The study presents succinic acid production from biomass of Miscanthus, integrated with downstream processing of fermentation broth. The pre-treatment procedure, used to loosen the lignocellulosic structure, was based on temperature (140 and 180 degrees C) and sulfuric acid addition (0.0, 0.5, 0.75, 1.0, 1.5 and 2.0% w/v). The pretreatment after addition of 1.5% H2SO4 at 140 degrees C ensured insignificant cellulose losses, the highest hemicellulose solubilization (60%) as well as effectively facilitated enzymatic saccharification (glucose yield: 80%). Succinic acid yield amounted to 73%, resulting in following mixture of carboxylic acids (% vol. of total acids): 64% succinic, 21% acetic and 15% formic acid. In the present study, an effective method of succinic acid (the target product) separation, using membrane processes (100-300 Da), was presented. Filtration using DK-NF membrane conducted at pH 6.8, followed by diafiltration, was selected as the most appropriate for the treatment of analysed fermentation broth. During diafiltration of retentate after NF treatment, the succinic acid content reached 95% of total acids present in the treated mixture. Whilst, the recovered permeate, containing mostly water, can be recycled and used again for biomass dilution in the pre-treatment step.