Abstract
The large use of conventional plastics has resulted in serious environmental problems. Polyhydroxyalkanoates represent a potent replacement to synthetic plastics because of their biodegradable nature. This study aimed to screen bacteria and archaea isolated from an extreme environment, the salt lake Chott El Jerid for the accumulation of these inclusions. Among them, two archaeal strains showed positive results with phenotypic and genotypic methods. Phylogenetic analysis, based on the 16S rRNA gene, indicated that polyhydroxyalkanoate (PHA)-producing archaeal isolates CEJGTEA101 and CEJEA36 were related to Natrinema altunense and Haloterrigena jeotgali, respectively. Gas chromatography and UV-visible spectrophotometric analyses revealed that the PHA were identified as polyhydroxybutyrate and polyhydroxyvalerate, respectively. According to gas chromatography analysis, the strain CEJGTEA101 produced maximum yield of 7 wt % at 37 °C; pH 6.5; 20% NaCl and the strain CEJEA36 produced 3.6 wt % at 37 °C; pH 7; 25% NaCl in a medium supplemented with 2% glucose. Under nutritionally optimal cultivation conditions, polymers were extracted from these strains and were determined by gravimetric analysis yielding PHA production of 35% and 25% of cell dry weight. In conclusion, optimization of PHA production from inexpensive industrial wastes and carbon sources has considerable interest for reducing costs and obtaining high yield.
Highlights
In recent decades, rapid population growth has increased the number of non-degradable materials
In our previous article [11], we presented a report of hydrolytic enzymes production by 35 extremely halophilic strains isolated from a mixture of waters and sediments of the Tunisian hypersaline ephemeral lake, Chott El Jerid [11]
Two archaeal strains CEJGTEA101 and CEJEA36 showed presence of black granules when stained with the lipophilic dye Sudan Black B and bright orange fluorescence under UV transilluminator when stained with the specific dye Nile Red
Summary
Rapid population growth has increased the number of non-degradable materials. To solve this problem, biodegradable polymers such as polyhydroxyalkanoates (PHAs) have attracted immense interest for several applications in industry, medicine, and agriculture because of their main characteristics of biodegradability and biocompatibility that allow PHAs used as an alternative to petroleum-based plastics [1]. Poly(3-hydroxybutyrate) (PHB) is the simplest homopolymer stored in prokaryotic cells [3]. This type is impermeable to oxygen, biodegradable, and biocompatible which make it a potential candidate for several applications [4]. Other PHA types, including poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and polyhydroxyoctanoate (PHO) are evaluated mainly for biomedicine [5]. The use of inexpensive carbon sources and waste products for PHA biosynthesis by halophiles is a good strategy and has been the subject of many investigations
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