Co-Production of Polyhydroxyalkanoates and Carotenoids by &lt;em&gt;Haloferax mediterranei&lt;/em&gt; DSM 1411

Beom Soo Kim,Chanin Khomlaem

doi:10.3390/cgpm2020-07175

Abstract

Polyhydroxyalkanoates (PHA) are naturally occurring biopolymers that possess high performance material properties such as biodegradability and biocompatibility. PHA can be produced from renewable carbon sources. However, the industrial production of PHA is still hindered by the costly feed materials. Co-production of other high-value products in addition to PHA can be helpful in alleviating overall production of PHA. In this work, the effect of temperature on PHA and carotenoids co-production by Haloferax mediterranei DSM 1411 was investigated using 1% glucose as carbon source. Under batch fermentation at 37°C, Haloferax mediterranei synthesized 3.37 g L-1 PHA with concomitant production of 0.76 mg L-1 of carotenoids at 144 h. The maximum dry cell weight (DCW) was 6.54 g L-1 and PHA content was 51.6%, with 3-hydroxyvalerate (3HV) fraction of 8.01 mol%. By increasing temperature to 42°C, an increase in PHA and carotenoids production was noticed reaching a maximum of 3.99 g L-1 and 0.92 mg L-1, respectively, at 120 h. Likewise, DCW was increased to 7.06 g L-1 and PHA content was 56.5%, with 3HV fraction of 8.42 mol%.

Highlights

Petrochemical-based plastics are widely used because of their good mechanical and thermal properties, constancy, and durability
Halobacterium medium consisting of NaCl 156 g L−1, MgCl2·6H2O 13 g L−1, MgSO4·7H2O 20 g L−1, CaCl2·6H2O 1 g L−1, KCl 4 g L−1, NaHCO3 0.2 g L−1, NaBr 0.5 g L−1, yeast extract 5 g L−1, agar 20 g L−1 with glucose 10 g L−1 was used for co-production of PHA and carotenoids by Haloferax mediterranei DSM 1411
This value was 26% higher than that recorded for Haloferax mediterranei culture incubated at 37 °C which indicates the positive effect of temperature on the growth of Haloferax mediterranei cells and accumulation of PHA as a growthassociated product [5]

Summary

Introduction

Petrochemical-based plastics are widely used because of their good mechanical and thermal properties, constancy, and durability. Many research has focused on the development and production of microbial-derived biodegradable polymers due to their low toxicity and high sustainability that will help to reduce plastic waste accumulation in the environment [1]. Microbial polyhydroxyalkanoates (PHA), a class of bio-based polymer with properties very similar to synthetic plastics, have attracted research and commercial interests worldwide because of their renewability, biocompatibility, and complete biodegradability [2]. The two most investigated types of PHA are poly(3-hydroxybutyrate) (PHB) and poly(3hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The introduction of 3-hydroxyvalerate (3HV) units to form PHBV disrupts the highly crystalline PHB structure, resulting in a polymer with enhanced mechanical properties, quicker degradation rates, and improved physical properties [3]

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