Lasiodiplodan, a (1→6)-β-d-glucan, is an exopolysaccharide with high commercial value and many applications in food, pharmaceuticals, and cosmetics. Current industrial production of β-glucans from crops is mostly by chemical routes generating hazardous and toxic waste. Therefore, alternative sustainable and eco-friendly pathways are highly desirable. Here, we have studied the lasiodiplodan production from sugarcane bagasse (SCB), a major lignocellulosic agricultural residue, by Lasiodiplodia theobromae CCT 3966. Lasiodiplodan accumulated on SCB hydrolysate (carbon source) supplemented with soybean bran or rice bran (nitrogen source) was 16.2 [6.8 × 103 Da] and 22.0 [7.6 × 103 Da] g/L, respectively. Lasiodiplodan showed high purity, low solubility, pseudoplastic behavior and was composed of glucose units. Moreover, the exopolysaccharides were substantially amorphous with moderate thermal stability and similar degradation temperatures. To our knowledge, this is the first report on the highest production of SCB-based lasiodiplodan to date. L. theobromae, as a microbial cell factory, demonstrated the commercial potential for the sustainable production of lasiodiplodan from renewable biomass feedstock.
Lasiodiplodan is a β-glucan polymer with different interesting characteristics, including therapeutic properties. It is an extracellular product, which is produced by the filamentous fungus Lasiodiplodia theobromae, using glucose as a substrate. In the present work, the production of lasiodiplodan was studied by the utilization of sugarcane straw as a low-cost carbon source. Glucose-rich sugarcane straw hydrolysate was obtained by a sequential pretreatment with dilute nitric acid (1% v/v) and sodium hydroxide (1% w/v), followed by enzymatic hydrolysis. The fermentation process was conducted by the cultivation of the strain Lasiodiplodia theobromae CCT3966 in sugarcane straw hydrolysate in a shake flask at 28 °C for 114 h. It was found that hydrolysate obtained after enzymatic hydrolysis contained 47.10 gL−1 of glucose. Fermentation experiments of lasiodiplodan synthesis showed that the peak yield and productivity of 0.054 gg−1 glucose consumed and 0.016 gL−1 h−1, respectively, were obtained at 72 h fermentation time. Fungal growth, glucose consumption, and lasiodiplodan production from sugarcane straw hydrolysate presented a similar pattern to kinetic models. The study on the chemical structure of lasiodiplodan produced showed it had a β-glucan construction. The current study revealed that sugarcane straw is a promising substrate for the production of lasiodiplodan.
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