Mining and fine-tuning sugar uptake system for titer improvement of milbemycins in .

Dramatic decrease of sugar uptake is a general phenomenon in at stationary phase, when antibiotics are extensively produced. Milbemycins produced by are a group of valuable macrolide biopesticides, while the low yield and titer impede their broad applications in agricultural field. Considering that inadequate sugar uptake generally hinders titer improvement of desired products, we mined the underlying sugar uptake systems and fine-tuned their expression in this work. First, we screened the candidates at both genomic and transcriptomic level in . Then, two ATP-binding cassette transporters named TP2 and TP5 were characterized to improve milbemycin titer and yield significantly. Next, the appropriate native temporal promoters were selected and used to tune the expression of TP2 and TP5, resulting in a maximal milbemycin A3/A4 titer increase by 36.9% to 3321 mg/L. Finally, TP2 and TP5 were broadly fine-tuned in another two macrolide biopesticide producers and , leading to a maximal titer improvement of 34.1% and 52.6% for avermectin B and nemadectin, respectively. This work provides useful transporter tools and corresponding engineering strategy for .