Enhanced production of poly glutamic acid by Bacillus sp. SW1-2 using statistical experimental design

Bacillus sp. SW1-2 producing poly glutamic acid (PGA), locally isolated from Eastern province in Saudi Arabia, was characterized and identified based on 16S rRNA gene sequencing. Phylogenetic analysis revealed its closeness to Bacillus megaterium. The homopolymer consists mainly of glutamic as indicated in the analysis of amino acid. Preliminary optimization of PGA production, through a series of one-variable-at-a-time (OVAT) experiments, revealed maximum PGA production of 10.5 (g/L). Statistically based experiments were applied to optimize culture conditions for production of PGA. Effect of 15 variables were examined for their significance on PGA production using Plackett-Burman factorial design. Among those variables; Na-citrate, (NH4)2SO4, glutamic acid and CaCl2.2H2O were most significant variables that encouraged PGA production, while those negatively affected were; glycerol, glucose and phosphate buffer. Significant parameters were further investigated using Box-Behnken design to define the optimal medium composition. Based on statistical analysis, maximal PGA production on optimized medium was 36.5 (g/L) which was more than 4-folds the basal production medium. Verification experiment was carried out to examine model validation and revealed more than 95% validity.Keywords: Poly glutamic acid, Bacillus megaterium, statistical experimental design, optimization, one-variable-at-a-time (OVAT)African Journal of Biotechnology Vol. 12(5), pp. 481-49

Perspectives of Polyhydroxyalkanoate (PHAs) Biopolymer Production Using Indigenous Bacteria: Screening and Characterization

There are wide range of biopolymers synthesized by diverse group of bacteria, among them intracellular polyhydroxyalkanoates (PHA) is on the priority list based on its higher level of uses and extensive studies on the processes involved in its biosynthesis. This study focused on screening of indigenous bacterial strains for PHA production. Twenty-six different indigenous bacterial strains have been inventoried and exploited for biopolymer production. The screened bacteria stained bluish-black to purple colonies upon staining with Sudan Black B indicating their potency for PHA production. The inclusion bodies produced strong orange fluorescence with staining by Nile Blue A which were further confirmed by microscopic examinations. The size distribution of PHA granules ranged from 0.5 to 1.0 ìm with the mean value of 0.5 ± 0.06 ìm. Out of 26 strains, Bacillus sp. Strain-6 and Pseudomonas sp. Strain-16 has been recognized as a potential candidate for biopolymer production and further identified through 16S rRNA gene analyses. The PHA yield of the two potent bacterial isolates being 0.84 and 1.12 g/L, and recorded 55.4 and 71.1% yield of PHA in cell dry weight (CDW), respectively. FT-IR Spectroscopic analysis of biopolymer produced by the two strains revealed two main absorptions peaks at C–H and carbonyl stretching bands characteristic to PHA. The H1 and C13 NMR spectra confirmed the presence of -CH- group in PHA extracted from the two strains

Possible Involvement of an Extracellular Superoxide Dismutase (SodA) as a Radical Scavenger in Poly(cis-1,4-Isoprene) Degradation▿

Gordonia westfalica Kb1 and Gordonia polyisoprenivorans VH2 induce the formation of an extracellular superoxide dismutase (SOD) during poly(cis-1,4-isoprene) degradation. To investigate the function of this enzyme in G. polyisoprenivorans VH2, the sodA gene was disrupted. The mutants exhibited reduced growth in liquid mineral salt media containing poly(cis-1,4-isoprene) as the sole carbon and energy source, and no SOD activity was detectable in the supernatants of the cultures. Growth experiments revealed that SodA activity is required for optimal growth on poly(cis-1,4-isoprene), whereas this enzyme has no effect on aerobic growth in the presence of water-soluble substrates like succinate, acetate, and propionate. This was detected by activity staining, and proof of expression was by antibody detection of SOD. When SodA from G. westfalica Kb1 was heterologously expressed in the sodA sodB double mutant Escherichia coli QC779, the recombinant mutant exhibited increased resistance to paraquat, thereby indicating the functionality of the G. westfalica Kb1 SodA and indirectly protection of G. westfalica cells by SodA from oxidative damage. Both sodA from G. polyisoprenivorans VH2 and sodA from G. westfalica Kb1 coded for polypeptides comprising 209 amino acids and having approximately 90% and 70% identical amino acids, respectively, to the SodA from Mycobacterium smegmatis strain MC2 155 and Micrococcus luteus NCTC 2665. As revealed by activity staining experiments with the wild type and the disruption mutant of G. polyisoprenivorans, this bacterium harbors only one active SOD belonging to the manganese family. The N-terminal sequences of the extracellular SodA proteins of both Gordonia species showed no evidence of leader peptides for the mature proteins, like the intracellular SodA protein of G. polyisoprenivorans VH2, which was purified under native conditions from the cells. In G. westfalica Kb1 and G. polyisoprenivorans VH2, SodA probably provides protection against reactive oxygen intermediates which occur during degradation of poly(cis-1,4-isoprene)

Dual-Functional Nanostructures for Purification of Water in Severe Conditions from Heavy Metals and <i>E. coli</i> Bacteria

Because of industrial water, many groundwater sources and other water bodies have a strongly acidic medium. Increased bacterial resistance against multiple antibiotics is one of the main challenges for the scientific society, especially those commonly found in wastewater. Special requirements and materials are needed to work with these severe conditions and treat this kind of water. In this trend, nanolayered structures were prepared and modified in different ways to obtain an optimum material for removing different kinds of heavy metals from water in severe conditions, alongside purifying water from a Gram-negative bacteria (E. coli), which is an indication for fecal pollution. An ultrasonic technique effectively achieved this dual target by producing nanolayered structures looking like nanotapes with dimensions of 25 nm. The maximum removal percentages of the heavy metals studied (i.e., iron (Fe), copper (Cu), chromium (Cr), nickel (Ni), and manganese (Mn)) were 85%, 79%, 68%, 63%, and 61%, respectively for one prepared structure. In addition, this nanostructure showed higher antimicrobial activity against the most common coliform bacterium, E. coli (inhibition zone up to 18.5 mm). This study introduces dual-functional material for removing different kinds of heavy metals from water in severe conditions and for treating wastewater for Gram-negative bacteria (E. coli)