Surfactin, which is composed of a β‐hydroxy fatty acid chain and a peptide ring, has drawn considerable attention due to its potential applications in the biomedicine, bioremediation, and petroleum industries. However, the low yield of surfactin from wild strains still restricts its industrial applications. In this study, eight genes relevant to the fatty acid biosynthesis pathway were targeted to enhance surfactin production, and high surfactin‐yielding strains with potential industrial applications were obtained. When ldeHA and acc were co‐overexpressed, the surfactin yield of recombinant strains TDS8 and TPS8 increased to 1.55‐ and 1.19‐fold of their parental strains, respectively, again proving that the conversion of acetyl‐coenzyme A (CoA) to malonyl‐CoA is the rate‐limiting step in fatty acid biosynthesis. Furthermore, changes in surfactin isoforms of recombinant strain TPS8 suggest that the fatty acid precursor synthesis pathway can be modified to improve the proportion of different isoforms. In addition, the deletion of lpdV, which is responsible for the conversion of α‐ketoacyl‐CoA precursors, resulted in a sharp decrease in surfactin production, further demonstrating the importance of branched‐chain fatty acid biosynthesis in surfactin production. This work will facilitate the design and construction of more efficiently engineered strains for surfactin production and further extend industrial applications.

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BackgroundLumbar disc herniation (LDH) is a common condition leading to high individual, social, and economic impacts. Reported rates of spontaneous resorption of LDH vary from 35% to 100%; however, it remains unclear how spontaneous absorption, rather than re-protrusion, can be maximized.Purpose The main objective of this study was to determine the characteristics and factors enabling for spontaneous regression of extruded LDH. DesignA retrospective single center case series. Patient sampleInpatients (n = 33) with LDH who experienced spontaneous regression between September 2015 and June 2020. Outcome measuresQuestionnaire responses and magnetic resonance imaging (MRI)-determined hernia regression.MethodsA questionnaire was distributed to patients to assess factors associated with hernia resorption, the volume of herniated intervertebral discs evaluated by MRI, and the absorption ratio calculated. Multiple linear regression was used to explore factors enabling spontaneous herniated disc regression. ResultsA total of 31 patients received a mean of 5.90 conservative treatments during hospitalization, and 1.91 during rehabilitation. Of patients, 90.32% underwent bed-rest during the acute phase of the disease, and 61.29% did so during rehabilitation. Rehabilitation exercise was undertaken by 93.55% of patients, with a mean of 2.42 exercise methods per patient. Waist lumbosacral orthosis devices were worn by 80.65% of patients. Multiple linear regression showed that bed-rest days in the acute phase (X1), herniation type (X2), time wearing lumbosacral orthosis (X3), onset-treatment duration (X4), and days of bed-rest days in rehabilitation (X5) had significant effects on the spontaneous regression ratio (y) of herniated discs (all P < 0.05). The optimal linear regression equation was y = 0.616 + 0.497X1 – 0.478X2 + 0.384X3 – 0.343X4 – 0.241X5. Conclusions Our findings support that patients with extruded or sequestered LDH should receive comprehensive treatment. Early treatment, early bed-rest, and lumbosacral orthosis protection promote the spontaneous regression of herniated discs; however, bed-rest during rehabilitation is a poor prognostic factor. Adherence to rehabilitation exercise will be beneficial to the recovery of patients with LDH.