Oxygen transfer rate during the production of alginate by Azotobacter vinelandii under oxygen-limited and non oxygen-limited conditions
Oxygen transfer rate during the production of alginate by Azotobacter vinelandii under oxygen-limited and non oxygen-limited conditions
复制标题
固氮菌在限氧和非限氧条件下生产海藻酸盐过程中的氧转移率
作者：
E. Lozano;E. Galindo;C. Peña
研究背景氧传递速率（OTR）和溶解氧张力（DOT）是影响海藻酸盐产量及其组成的重要因素，但OTR和DOT对海藻酸盐产量和组成的影响尚未见系统研究。本文报道了一项关于野生型A.藻酸盐生产及其聚合物分子量演变的研究。vinelandii菌株ATCC 9046，在溶解氧张力（DOT）保持恒定的培养物中的最大氧转移速率（OTRmax）方面。结果显示，在两种评估的溶解氧条件下，通过气体混合严格控制在0.5%和5%DOT，搅拌速度的增加（从300到700 rpm）导致OTRmax显著增加（对于5%的DOT，从17至100 mmol L-1 h-1，对于0.5%的DOT，从6至70 mmol L-1 h-1）。这种OTRmax的增加提高了藻酸盐的生产，以及特定的藻酸盐生产速率（SAPR），在100 mmol L-1 h-1的OTRmax下，培养物中的最大藻酸盐浓度达到3.1 g L-1，SAPR达到0.031 g alg g biom-1 h-1。相比之下，从非限氧条件下培养的培养物中分离的藻酸盐的平均分子量（MMM）通过降低OTRmax而增加，在OTRmax为17 mmol L-1 h-1时达到最大550 kDa。然而，在氧气限制下发展的文化中，（0.5%DOT）时，聚合物的MMM实际上相同结论总的来说，我们的结果表明，在氧限制和非氧限制条件下，藻酸盐的产生及其分子量与OTRmax有关，与文化的DOT无关。
BackgroundThe oxygen transfer rate (OTR) and dissolved oxygen tension (DOT) play an important role in determining alginate production and its composition; however, no systematic study has been reported about the independent influence of the OTR and DOT. In this paper, we report a study about alginate production and the evolution of the molecular mass of the polymer produced by a wild-type A. vinelandii strain ATCC 9046, in terms of the maximum oxygen transfer rate (OTRmax) in cultures where the dissolved oxygen tension (DOT) was kept constant.ResultsThe results revealed that in the two dissolved oxygen conditions evaluated, strictly controlled by gas blending at 0.5 and 5% DOT, an increase in the agitation rate (from 300 to 700 rpm) caused a significant increase in the OTRmax (from 17 to 100 mmol L-1 h-1 for DOT of 5% and from 6 to 70 mmol L-1 h-1 for DOT of 0.5%). This increase in the OTRmax improved alginate production, as well as the specific alginate production rate (SAPR), reaching a maximal alginate concentration of 3.1 g L-1 and a SAPR of 0.031 g alg g biom-1 h-1 in the cultures at OTRmax of 100 mmol L-1 h-1. In contrast, the mean molecular mass (MMM) of the alginate isolated from cultures developed under non-oxygen limited conditions increased by decreasing the OTRmax, reaching a maximal of 550 kDa at an OTRmax of 17 mmol L-1 h-1 . However, in the cultures developed under oxygen limitation (0.5% DOT), the MMM of the polymer was practically the same (around 200 kDa) at 300 and 700 rpm, and this remained constant throughout the cultivation.ConclusionsOverall, our results showed that under oxygen-limited and non oxygen-limited conditions, alginate production and its molecular mass are linked to the OTRmax, independently of the DOT of the culture.