Poly-3-hydroxybutyrate (P3HB) is a biopolymer, which presents characteristics similar to those of plastics derived from the petrochemical industry. The thermomechanical properties and biodegradability of P3HB are influenced by its molecular weight (MW). The aim of the present study was to evaluate the changes of the molecular weight of P3HB as a function of oxygen transfer rate (OTR) in the cultures using two strains of Azotobacter vinelandii, a wild-type strain OP, and PhbZ1 mutant with a P3HB depolymerase inactivated. Both strains were grown in a bioreactor under different OTR conditions. An inverse relationship was found between the average molecular weight of P3HB and the OTR_max, obtaining a polymer with a maximal MW (8000–10,000 kDa) from the cultures developed at OTR_max of 5 mmol L⁻¹ h⁻¹ using both strains, with respect to the cultures conducted at 8 and 11 mmol L⁻¹ h⁻¹, which produced a P3HB between 4000 and 5000 kDa. The increase in MW of P3HB was related to the activity of enzymes involved in the synthesis and depolymerization. Overall, our results show that it is possible to modulate the average molecular weight of P3HB by manipulating oxygen transfer conditions with both strains (OP and PhbZ1 mutant) of A. vinelandii.

聚-3-羟基丁酸酯（P3HB）是一种生物聚合物，具有与石油化学工业生产的塑料相似的特性。P3HB的分子量（MW）影响其热机械性能和生物降解性。本研究的目的是评估使用两种葡萄固氮菌菌株，野生型菌株OP和带有P3HB的PhbZ1突变体在培养物中P3HB分子量随氧气传输速率（OTR）的变化。解聚酶失活。两种菌株均在不同OTR条件下在生物反应器中生长。在P3HB的平均分子量和OTR _max之间发现反比关系，从OTR开发的培养物中获得最大分子量（8000–10,000 kDa）的聚合物相对于在8和11 mmol L ^-1  h ^-1进行的培养，使用这两个菌株_最多可产生5 mmol L ^-1  h ^-1，产生的P3HB在4000和5000 kDa之间。P3HB的MW增加与参与合成和解聚的酶的活性有关。总的来说，我们的结果表明，有可能通过与两种菌株（OP和PhbZ1突变体）操纵氧转移条件来调节P3HB的平均分子量A.固氮菌。