Sustainable production of camptothecin from an Alternaria sp. isolated from Nothapodytes nimmoniana

Rahul Kanumuri,I A H Khwajah Mohinudeen,Suresh Kumar Rayala,K N Soujanya,R Uma Shaanker,Smita Srivastava

doi:10.1038/s41598-020-79239-5

Abstract

Camptothecin the third most in demand alkaloid, is commercially extracted in India from the endangered plant, Nothapodytes nimmoniana. Endophytes, the microorganisms that reside within plants, are reported to have the ability to produce host–plant associated metabolites. Hence, our research aims to establish a sustainable and high camptothecin yielding endophyte, as an alternative source for commercial production of camptothecin. A total of 132 endophytic fungal strains were isolated from different plant parts (leaf, petiole, stem and bark) of N. nimmoniana, out of which 94 were found to produce camptothecin in suspension culture. Alternaria alstroemeriae (NCIM1408) and Alternaria burnsii (NCIM1409) demonstrated camptothecin yields up to 426.7 ± 33.6 µg/g DW and 403.3 ± 41.6 µg/g DW, respectively, the highest reported production to date. Unlike the reported product yield attenuation in endophytes with subculture in axenic state, Alternaria burnsii NCIM1409 could retain and sustain the production of camptothecin up to ~ 200 μg/g even after 12 continuous subculture cycles. The camptothecin biosynthesis in Alternaria burnsii NCIM1409 was confirmed using 13C carbon labelling (and cytotoxicity analysis on different cancer cell lines) and this strain can now be used to develop a sustainable bioprocess for in vitro production of camptothecin as an alternative to plant extraction.

Highlights

Camptothecin the third most in demand alkaloid, is commercially extracted in India from the endangered plant, Nothapodytes nimmoniana
254.1 ± 17.9 μg/g DW in cultures developed from the second generation slant, this endophyte demonstrated a steady yield of ~ 200 μg/g DW in cultures from 3rd till 12th generation slant. These results demonstrate that the highest yielding strain may not always be a sustainable producer, and it is important to consider sustainable production along with product yield of the metabolite during the screening and selection of a potential endophyte for successful bioprocess development
A microbial fermentation process, which is amenable to optimization and scale-up for enhanced yield and productivity, can be an excellent alternative to the natural plant source for large-scale and sustainable production of camptothecin under in vitro conditions

Summary

Introduction

Camptothecin the third most in demand alkaloid, is commercially extracted in India from the endangered plant, Nothapodytes nimmoniana. Our research aims to establish a sustainable and high camptothecin yielding endophyte, as an alternative source for commercial production of camptothecin. The camptothecin biosynthesis in Alternaria burnsii NCIM1409 was confirmed using 13C carbon labelling (and cytotoxicity analysis on different cancer cell lines) and this strain can be used to develop a sustainable bioprocess for in vitro production of camptothecin as an alternative to plant extraction. Camptothecin, first reported in 19661, is a monoterpene indole alkaloid It is commercially produced from plants, mainly Camptotheca acuminata and Nothapodytes nimmoniana[2]. Since the discovery of the first taxol producing e ndophyte[8], endophytes in general have gained attention as a potent alternative source of plant metabolites.

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Conclusion