Optimization of complex medium composition for heterotrophic cultivation of Euglena gracilis and paramylon production

Abstract

Heterotrophic cultivation of Euglena gracilis was carried out on synthetic (Hutner medium) and complex cultivation media in order to optimize production of β-1,3-glucan (paramylon). For preparation of complex media, various industrial by-products (e.g., molasses, corn steep solid, yeast extract, and beef extract) were used with or without addition of pure compounds [glucose, galactose, fructose, lactose, maltose, sucrose, and (NH4)2HPO4]. Heterotrophic cultivation of E. gracilis was performed in Erlenmeyer flasks and additionally confirmed during research in the stirred tank bioreactor. The results clearly show that E. gracilis can easily metabolize glucose and fructose as carbon sources and corn steep solid as complex nitrogen and growth factors source for biomass growth and paramylon synthesis. Furthermore, it was also proved that addition of (NH4)2HPO4, beef extract, or gibberellic acid did not have positive effect on the biomass growth and paramylon synthesis. After optimization of complex medium composition and verification in the stirred tank bioreactor, it was concluded that medium composed of glucose (20 g/L) and corn steep solid (30 g/L) is the most suitable complex medium for industrial cultivation of E. gracilis and paramylon production.

Comparative assessment of the Euglena gracilis var. saccharophila variant strain as a producer of the β‐1,3‐glucan paramylon under varying light conditions

“…This is higher than the most commonly reported 50%–60% (Šantek et al. , Ivušić and Šantek , Ogawa et al. ) and on par with the 75% achieved with repeated‐batch cultivation of the Z strain with an oversupply of glucose (Šantek et al.…”

“…, Grimm et al. , Ivušić and Šantek ). Other approaches to increase volumetric production of paramylon using very high amounts of glucose and other complex carbohydrate sources have returned much lower Y par/glu values (Šantek et al.…”

Genotoxicity and subchronic toxicity evaluation of dried Euglena gracilis ATCC PTA-123017

“…In the absence of substantial historical evidence establishing a history of safe food use for a particular microbial species, as exists for common microorganisms such as Baker's yeast (Saccharomyces cerevisiae) or lactic acid bacteria, the safety assessment of a new microorganism -or constituent derived thereof -intended for introduction to the food supply must be supported by appropriate toxicological data characterizing the commercial organism of interest. In rare cases some species are known to be so genetically and phenotypically monomorphic (e.g., Bifidobacterium animalis) that safety information available for a particular strain can be extrapolated to other members within the species; however, in general most microbial species, including E. gracilis, have heterotrophic phenotypes that are highly influenced by environmental factors and culture conditions (Schneider and Betz, 1985;Rodríguez-Zavala et al, 2010;Ivu si c and Santek, 2015). Therefore, safety information is typically required for each new strain that is intended for food use.…”

Heterotrophic cultivation of Euglena gracilis on chemically pretreated media

“…Bioprocess efficiency parameters [biomass production (X T ), conversion yield (Y X/S ) and productivity (Pr)] were calculated by standard procedures (Ivušić and Šantek, 2015).…”

“…E. gracilis is also capable of growing on several carbon sources and it has even been shown that it can grow on potato liquor and corn steep solids based media. The aim of these studies was to define simple and inexpensive complex media suitable for large scale heterotrophic cultivation of Euglena gracilis and paramylon production (Šantek et al, 2010;Šantek et al, 2012;Ivušić and Šantek, 2015). Medium type (composition) and medium optimization are highly important parts of any bioprocess as they can substantially reduce time and costs, as well as increase the bioprocess performance efficiency (Kennedy and Krouse, 1999).…”