Benzoic acid fermentation from starch and cellulose via a plant-like β-oxidation pathway in <it>Streptomyces maritimus</it>

<p>Abstract</p> <p>Background</p> <p>Benzoic acid is one of the most useful aromatic compounds. Despite its versatility and simple structure, benzoic acid production using microbes has not been reported previously. <it>Streptomyces</it> are aerobic, Gram-positive, mycelia-forming soil bacteria, and are known to produce various kinds of antibiotics composed of many aromatic residues. <it>S. maritimus</it> possess a complex amino acid modification pathway and can serve as a new platform microbe to produce aromatic building-block compounds. In this study, we carried out benzoate fermentation using <it>S. maritimus</it>. In order to enhance benzoate productivity using cellulose as the carbon source, we constructed endo-glucanase secreting <it>S. maritimus</it>.</p> <p>Results</p> <p>After 4 days of cultivation using glucose, cellobiose, or starch as a carbon source, the maximal level of benzoate reached 257, 337, and 460 mg/l, respectively. <it>S. maritimus</it> expressed β-glucosidase and high amylase-retaining activity compared to those of <it>S. lividans</it> and <it>S. coelicolor</it>. In addition, for effective benzoate production from cellulosic materials, we constructed endo-glucanase-secreting <it>S. maritimus</it>. This transformant efficiently degraded the phosphoric acid swollen cellulose (PASC) and then produced 125 mg/l benzoate.</p> <p>Conclusions</p> <p>Wild-type <it>S. maritimus</it> produce benzoate via a plant-like β-oxidation pathway and can assimilate various carbon sources for benzoate production. In order to encourage cellulose degradation and improve benzoate productivity from cellulose, we constructed endo-glucanase-secreting <it>S. maritimus.</it> Using this transformant, we also demonstrated the direct fermentation of benzoate from cellulose. To achieve further benzoate productivity, the L-phenylalanine availability needs to be improved in future.</p>