Abstract
Increased interest in marine resources has led to increased screening of marine fungi for novel bioactive compounds and considerable effort is being invested in discovering these metabolites. For compound discovery, small-scale cultures are adequate, but agitated bioreactors are desirable for larger-scale production. Calcarisporium sp. KF525 has recently been described to produce calcaride A, a cyclic polyester with antibiotic activity, in agitated flasks. Here, we describe improvements in the production of calcaride A in both flasks (13-fold improvement) and stirred bioreactors (200-fold improvement). Production of calcaride A in bioreactors was initially substantially lower than in shaken flasks. The cultivation pH (reduced from 6.8 to <5.4), carbon source (sucrose replacing glucose), C/N ratio and nature of mycelial growth (pellets or filaments) were important in improving calcaride A production. Up to 4.5 mg·g−1 biomass (85 mg·L−1) calcaride A were produced in the bioreactor, which was only slightly less than in shaken flasks (14 mg·g−1, 100 mg·L−1). The results demonstrate that a scalable process for calcaride A production could be developed using an iterative approach with flasks and bioreactors.
Highlights
Organisms from marine environments, especially marine bacteria, actinomycetes, dinoflagelates, invertebrates and sponges, and fungi, are recognized as good sources of novel, bioactive compounds [1,2,3]
Marine fungi produce a wide range of novel bioactive compounds and considerable effort is being invested in discovering these metabolites [4]
To assess whether the carbon source affected calcaride A production, KF525 was grown in defined medium with glucose, sucrose, fructose, maltose, lactose, malt extract or starch as the carbon source, with ammonium as the nitrogen source
Summary
Organisms from marine environments, especially marine bacteria, actinomycetes, dinoflagelates, invertebrates and sponges, and fungi, are recognized as good sources of novel, bioactive compounds [1,2,3]. Marine fungi produce a wide range of novel bioactive compounds and considerable effort is being invested in discovering these metabolites [4]. Calcarisporium species (e.g., C. arbuscula) are generally isolated as endophytes or parasites from agarics (Basidiomycetes) or higher Ascomycetes or from wood [9], but are occasionally isolated from marine environments [10]. Extracts from some species have been used as feed preservative [11] and bioactive compounds (e.g., macrocyclic trichothecenes, sesquiterpene esters, and sterols) have been identified from several isolates [12,13,14,15]. Related compounds are reported to have antifungal activity [17], but the bioactivity of calcaride A has not been extensively investigated. The growth characteristics of Calcarisporium species are poorly described. KF525 and production of one of the five calcaride products, using calcaride A as an indicator of general calcaride production
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