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This study demonstrated the importance of fermentation broth pretreatment and dewatering by forward osmosis (FO) before keto carboxylic acid recovery. The most effective and profitable pretreatment procedure was a combination of centrifugation, ceramic ultrafiltration of molecular weight cut-off of 15 kDa, and ceramic nanofiltration of molecular weight cut-off of 450 Da. By applying the complex pretreatment and FO as a pre-concentration step of fermentation broth dewatering, the keto acid enrichment of two times was achieved for alpha-ketoglutaric acid and pyruvic acid. Extensive fouling analysis performed in this study confirmed that the proposed pretreatment procedure was sufficient to avoid severe fouling of the FO dewatering process. A techno-economic analysis of the proposed keto acid extraction scheme shown that by using FO for fermentation broth dewatering, the total capital investment was reduced and the payback time was shortened by 0.83 yr. [Display omitted] • FO fouling reduction & keto acid enrichment governed pretreatment selection. • The best pretreatment was a combination of centrifugation, UF, and loose NF. • Keto acid enrichment of 2 times was achieved by pretreatment and FO dewatering. • FO dewatering reduced capital investment & shortened the payback time by 0.83 yr. [ABSTRACT FROM AUTHOR]

Abstract: Cross-flow microfiltration of fermented mash containing native corn starch granules from a simultaneous saccharification and fermentation process, was investigated with respect to the process performance. Influence of transmembrane pressure and cross-flow velocity on normalized permeate flux rate decline and membrane fouling were examined. The microfiltration system was equipped with a tubular ceramic membrane with 0.45μm pore size. A combined pore-blockage–cake-filtration model was successfully used to determine the process performance and identify principal fouling mechanisms. Experimental results revealed that the fouling phenomenon taking place during microfiltration of the fermented mash follows a pattern of initial complete pore blockage and subsequent cake formation. As a result, initial rapid flux decline is followed by gradual flux decline. Fouled membranes were characterized using scanning electron microscopy (SEM). The membrane surface characteristics examined by SEM images evidenced formation of dense deposit on the upper membrane surface. Rinsing the fouled membrane with water followed by investigation of the permeate flux rate indicated occurrence of increased fouling, when microfiltration was carried out at high transmembrane pressure. The highest normalized flux decline was observed for microfiltration operated at the highest transmembrane pressure (1.4bar) and the lowest cross flow velocity (1ms−1). It is recommended to use high cross-flow velocity (4.55ms−1) and low transmembrane pressure (0.35bar) to minimize membrane fouling, triggered by components of the fermented mash. [Copyright &y& Elsevier]

Abstract: The economic competitiveness of fuel ethanol in comparison with fossil fuels depends on the effective lowering of costs on each step of the process. One of the most promising methods seems to be the application of membrane separation technology. In this study, the focus is on improvement of brewer''s wort fermentation. For this purpose, the membrane distillation process for ethanol recovery was implemented. The experimental system consisted of a bioreactor equipped with a capillary polypropylene microfiltration unit. Yeast cells’ count and viability, assimilation of sugars, production of ethanol and fermentation of by-products (glycerol and lactic acid) were monitored during fermentations. The intercellular trehalose as well as Hsp70 and Hsp104 heat shock proteins contents were determined. It was concluded that membrane distillation can be regarded as a straightforward method, which leads to an increase in ethanol production by facilitation of the continuous process, more complete fermentation of sugars, lowering the osmotic pressure in the fermentation broth, decreasing glycerol synthesis level and increasing yeast cells’ number and viability. [Copyright &y& Elsevier]