Effects of a combination of glucose and xylose on L-ornithine

Metabolism of different sugars is an important basement for the lignocellulose utilization. Glucose and xylose are the most important six- and five-carbon sugars in the hydrolysis of lignocellulose. We compared L-ornithine yield in different ratios of glucose and xylose in the case of the total sugar concentration was constant. On the premise that the total sugar concentration is 100 g/L, seven groups of different glucose concentration gradients were chosen (Fig.5). The mixed carbon sources showed the advantage of L-ornithine yield compared with using glucose or xylose as the sole carbon source. The results showed that the maximum L-ornithine production could be obtained (41.5 ± 0.02 g/L) when glucose is 70 g/L and xylose is 30 g/L (Fig.5 b, c).
Based on all the above conditions, the OD600 and L-ornithine production of strain XAB03 could reach to 16.8 ± 0.19 and 41.5 g/L (Fig.6c) respectively after shake flask fermentation for 72h, which is the highest titer so far to the best of our knowledge (Table 2), 7.8% higher than Zhang et al. had reported, and increased by 43.4% compared with the sole xylose carbon source (Zhang et al., 2019). The 2:1 ratio is close to the ratio of glucose to xylose after lignocellulose hydrolysis. This result lays a foundation for the feasibility and superiority of L-ornithine synthesis from lignocellulose hydrolysate.