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4. Overproduction of poly(3-hydroxybutyrate) by the extremely halophilic archaeon Haloarculasp.CEJ40-10 using starchy substrate

Author

Ben Abdallah, Manel, Sayadi, Sami, and Karray, Fatma

Abstract

Polyhydroxyalkanoates (PHAs), green alternatives to petroleum-derived plastics, possess desired features that make them preferred for various applications. Poly(3-hydroxybutyrate) (PHB), one of the most known representative of PHAs, could be synthesized by haloarchaeal species but their production amounts are relatively low compared to those of poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) obtained by haloarchaea. This is the first report describing an overproduction of PHB by a wild-type halophilic archaeon isolated from southern Tunisia, Chott El Jerid. According to the 16S rRNA gene sequence analysis, the isolate CEJ40-10 was affiliated with the species of the genus Haloarcula(97.5% similarity). Regarding the phylogeny based on the amino acid sequences of the PHA synthase subunits encoded by phaCand phaE, their identities to those from Haloarcula quadratawere 99% and 100%, respectively. This strain could accumulate maximum PHA using 1% (w/v) starch at pH 6, after incubation for 72 h at 37 °C with high salt content (30% NaCl). The replacement of starch with glucose or sugar wastewater lowered the polymer yield. Four extraction methods were performed in order to achieve the maximum efficiency of polymer recovery. Hypochlorite digestion of biomass gave a high recovery yield, reaching 72.8% of its total dry mass. Furthermore, analytical methods such as the Fourier transform infrared (FTIR) spectroscopy, gas chromatography (GC), and UV–visible spectrophotometry indicated that the composition of the polymer was a homopolymer PHB. Our findings showed that Haloarculasp.strain CEJ40-10 was a potential PHB-candidate for industrial scale production using starchy substrates.

Published
2024
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8. Production of Polyhydroxyalkanoates by Two Halophilic Archaeal Isolates from Chott El Jerid Using Inexpensive Carbon Sources

Author

Ben Abdallah, Manel, Karray, Fatma, and Sayadi, Sami

Subjects
pha-producing archaea, Halobacteriaceae, hypersaline lake, Polyhydroxyalkanoates, PHA-producing archaea, lcsh:QR1-502, polyhydroxyalkanoate, carbon sources, biodegradable polymer, Article, Carbon, lcsh:Microbiology, RNA, Ribosomal, 16S, Phylogeny
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.

Published
2020

12. Anaerobic biological treatment of industrial saline wastewater: fixed bed reactor performance and analysis of the microbial community structure and abundance.

Author

Jeddi, Mariem, Karray, Fatma, Loukil, Slim, Mhiri, Najla, Ben Abdallah, Manel, and Sayadi, Sami

Subjects
MICROBIAL communities, FIXED bed reactors, SEWAGE, TUNA, BIOGAS production, ENVIRONMENTAL impact charges, UPFLOW anaerobic sludge blanket reactors
Abstract

The purpose of the present work is to treat saline Tuna fish wastewater, with the salt concentration of 43 g L−1 and total organic carbon (TOC) of 8.3 g L−1, using an anaerobic fixed bed reactor involving salt-tolerant bacteria from the natural hypersaline environment during 150 days. The highest volatile solids (VS) removal efficiency of 84.1% was recorded for the organic loading rate (OLR) of 1.04 g TOC L−1.d−1 and the lowest salinity of 14.6 g NaCl L−1. In addition, the maximum biogas production of 0.8 L−1.d−1 for a working volume of 4 L and an organic loading rate of 2.07 g TOC L−1.d−1 correlated with the decrease of Volatile fatty acids (VFA) content. The Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) and the phylogenetic analysis of the bacterial community showed the action of hydrolytic, acidogenic, halotolerant sulfate-reducing and halophilic fermentative bacterium during the processing time. A stable archaeal and methanogenic community's diversity including hydrogenotrophic methanogens was demonstrated with Quantitative-PCR (Q-PCR). The highest bacterial population abundance was detected for 1.45 g TOC L−1.d−1 and the important methanogenic community abundance for 2.07 g TOC L−1.d−1 may be related to the highest biogas production in this charge for an effluent salinity of 27.7 g NaCl L−1. [ABSTRACT FROM AUTHOR]

Published
2020
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