Spinosyn D

Spinosyns are natural broad-spectrum biological insecticides with a double glycosylated polyketide structure that are produced by aerobic fermentation of the actinomycete,Saccharopolyspora spinosa.However, their large-scale overproduction is hindered by poorly understood bottlenecks in optimizing the original strain, and poor adaptability of the heterologous strain to the production of spinosyn. In this study, we genetically engineered heterologous spinosyn-producerStreptomyces albusJ1074 and optimized the fermentation to improve the production of spinosad (spinosyn A and spinosyn D) based on our previous work. We systematically investigated the result of overexpressing polyketide synthase genes (spnA,B,C,D,E) using a constitutive promoter on the spinosad titer inS. albusJ1074. The supply of polyketide synthase precursors was then increased to further improve spinosad production. Finally, increasing or replacing the carbon source of the culture medium resulted in a final spinosad titer of ~70 mg/L, which is the highest titer of spinosad achieved in heterologousStreptomycesspecies.This research provides useful strategies for efficient heterologous production of natural products.

The dissipation and residues of an eco-friendly bio-pesticide, spinosad, in cowpea under field conditions were studied using ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MSMS) after Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction. The method exhibited good linearity with respect to spinosyn A and spinosyn D in solvent or blank cowpea matrix with correlation coefficients>0.99. Additionally, matrix effects were not significant in the range 0.987-1.014, and the average recoveries at three concentration levels were 75.1-91.1 and 79.4-90.5% for spinosyn A and spinosyn D, respectively. The intra- and inter-day relative standard deviations were 2.5-9.3 and 7.8-9.8% for spinosyn A, respectively, and 4.1-7.9 and 6.6-8.3% for spinosyn D, respectively. The limits of detection (LODs) and limits of quantification (LOQs) were 0.005 and 0.01 mg kg(-1), respectively, for spinosyn A, and 0.002 and 0.005 mg kg(-1), respectively, for spinosyn D. The dissipation of spinosad (sum of spinosyn A and spinosyn D) fitted well to first-order kinetics with half-lives of 0.9-1.5 days. The highest residue (HR) at pre-harvest interval (PHI) of 12 h was 0.321 mg kg(-1). Compared with the maximum residue limit (MRL) set by Codex, a PHI of at least 24 h was recommended. The estimated daily chronic intake of spinosad from cowpea was less than 0.14% of the acceptable daily intake (ADI). Therefore, the risk of consuming cowpea sprayed with spinosad under recommended field conditions was considered acceptable for the Chinese population.

Spinosad 0.9% suspension is a topical treatment for head-lice infestation (pediculosis capitis) that has been approved in the US as a prescription medicine. Spinosad is a natural mixture of the pediculicidal tetracyclic macrolides spinosyn A and spinosyn D. Spinosad 0.9% mainly interferes with nicotinic acetylcholine receptors in insects, thereby producing neuronal excitation that results in paralysis of lice from neuromuscular fatigue after extended periods of hyperexcitation. Spinosad 0.9% kills both permethrin-susceptible and permethrin-resistant populations of lice. It is also ovicidal, killing both eggs (nits) and lice. Systemic absorption was not detectable after a single topical application of spinosad 1.8% for 10 minutes in children. In randomized, evaluator-blind, multicenter clinical trials, topical spinosad 0.9% without nit combing was significantly more effective than permethrin 1% with nit combing in the eradication of head lice assessed 14 days after one or two treatments. The majority of subjects treated with spinosad 0.9% without nit combing required only a single treatment to eradicate head lice, while the majority of those treated with permethrin 1% with nit combing required two treatments. Spinosad was generally well tolerated in clinical trials, with no severe or serious adverse events. Cutaneous and ocular irritation were the most common adverse events.

Spinosyn and its analogs, produced by Saccharopolyspora spinosa, are the active ingredients in a family of insect control agents. They are macrolides with a 21-carbon, 12-membered tetracyclic lactones that are attached to two deoxysugars, tri-O-methylrhamnose and forosamine. Labeling studies, analysis of the biosynthetically blocked mutants, and the genetic identification of the spinosyn gene cluster have provided detailed information concerning the mechanism of spinosyn biosynthesis and have enabled combinatorial biosynthesis of a large group of new spinosyns. The following developments have recently impacted the field of spinosyn biology: (1) A second-generation spinosyn called spinetoram (XDE-175) was launched in late 2007; it is a semisynthesized spinosyn derivative produced through the modification of 3'-O-methyl group of rhamnose and the double bond between C5 and C6 of spinosyn J and L. This molecule was shown to have improved insecticidal activity, enhanced duration of control, and an expanded pest spectrum. (2) A new class of spinosyns, the butenyl-spinosyns, was discovered from Saccharopolyspora pogona. The butenyl-spinosyns are similar to spinosyns, but differ in the length of the side chain at C-21. In addition to structural similarities with the spinosyns, the butenyl-spinosyns exhibit a high level of similarity in insecticidal activity to spinetoram. (3) Spinosyn analogs, 21-cyclobutyl-spinosyn A and 21-cyclobutyl-spinosyn D were generated by metabolic engineering of the spinosyn biosynthetic gene cluster. They showed better insecticidal activities against cotton aphid and tobacco budworm than that of spinosyn A and D. Future progress toward the development of more potent spinosad analogs, as well as enhancements in production yields will likely result from these recent advances in the genetics and biochemistry of spinosyns.