Using methane-arrested mixed cultures, organic substrates can be fermented to mixed carboxylic acids (i.e., C2 to C8 volatile fatty acids) via the carboxylate platform. A commercial example, the MixAlco® process recovers the carboxylic acids and transforms them to chemicals and fuels. To reduce product inhibition, ion-exchange resin (IR) fermentors used weak-base anion-exchange resins (Amberlite IRA-67) to recover carboxylic acids from fermentation broth and thereby maintain near-neutral pH. Control fermentors used magnesium carbonate (MgCO₃) to buffer to near-neutral pH. Compared to the control, the IR fermentors increased acid yields by 2.2, 1.54, and 1.55 times for α-cellulose substrate, paper substrate, and lime-pretreated corn stover, respectively. Furthermore, extraction increased yields of valuable long-chain carboxylic acids. These results suggest further improvements are possible in advanced MixAlco® process configurations, such as countercurrent continuous fermentations.

使用抑制甲烷的混合培养物，有机底物可以通过羧酸盐平台发酵成混合羧酸（即 C2 至 C8 挥发性脂肪酸）。一个商业示例，MixAlco® 工艺回收羧酸并将其转化为化学品和燃料。为了减少产物抑制，离子交换树脂 (IR) 发酵罐使用弱碱阴离子交换树脂 (Amberlite IRA-67) 从发酵液中回收羧酸，从而保持接近中性的 pH 值。对照发酵罐使用碳酸镁 (MgCO ₃) 缓冲至接近中性的 pH 值。与对照相比，IR 发酵罐对 α-纤维素基质、纸基质和石灰预处理的玉米秸秆的酸产量分别提高了 2.2、1.54 和 1.55 倍。此外，提取增加了有价值的长链羧酸的产量。这些结果表明在先进的 MixAlco® 工艺配置中可以进一步改进，例如逆流连续发酵。