改写以下段落可以调整语序更换用词。要求逻辑清晰、用词精准、语句通顺符合科研论文表达：细菌素作为细菌的次级代谢产物通常产量很低。粗提取应该尽可能将发酵上清中的细菌素进行分离浓缩。目前常用的方法包括有机试剂萃取、盐析、膜分离和pH吸附-解吸附法等。

As a secondary metabolite of bacteria, bacteriocin usually has low yield. Therefore, it is necessary to separate and concentrate bacteriocin from the fermentation broth as much as possible in crude extraction. Currently, common methods include organic solvent extraction, salt precipitation, membrane separation, and pH adsorption-desorption.