Efficacy of Cavern Isolates for Biodegradation of Synthetic Plastic

: Synthetic plastic waste management is a tenacious environmental concern at the global level. Although all types of synthetic plastics are a nuisance to the environment, however, versatility and one time use have made polyethylene (PE) a foremost environmental issue. The current study has investigated cavern bacterial strains isolated from PE samples from San Giovanni cave, Sardinia, Italy for their efficacy to biodegrade low-density polyethylene (LDPE) film. It was an initial effort to use cavern bacteria in plastic biodegradation studies. Chemical and physical changes in the composition of LDPE were studied by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) after incubation with the bacterial consortium for two months. Collected cavern PE plastic samples were also studied for biodegradation after incubation in nutrient broth for two months. FTIR revealed obvious signs of degradation with the appearance of two new peaks of functional groups, nitriles (C≡N) and amines (N-H) in LDPE film, which are intermediate metabolites of β- oxidation pathway. An increase in various existing peaks of several intermediate metabolites including aldehydes, ketones, alcohols, and carboxylic acids, were also observed in experimental LDPE compared to control. Peaks of alkanes decreased significantly owing to cavern bacterial activity. SEM revealed biofilm formation on experimental LDPE surface with substantial mechanical damage. Similar signs of degradation were observed in the cavern PE samples. Four bacterial strains in the current consortium, including Bacillus sonorensis, Bacillus subtilis, Aneurinibacillus spp., and Alcaligenes faecalis are first time reported to be linked with biodegradation of plastics. The cavern bacteria under study have the potential to biodegrade LDPE.

Improvement of Unconfined Compressive Strength of Soft Clay using Microbial Calcite Precipitates

The precipitation of calcite induced via microorganisms (MICP) is a technique that has been developed as an innovative sustainable ground improvement method utilizing ureolytic bacteria to soil strengthening and stabilization. Locally isolated Bacillus Sonorensis from Iraqi soil samples were found to have high abilities in producing urease. This study aims to use the MICP technique in improving the undrained shear strength of soft clay soil using two native urease producing bacteria that help in the precipitation of calcite to increase the cementation between soil particles. Three concentrations of each of the locally prepared Bacillus sonorensis are used in this study for cementation reagent (0.25M, 0.5M, and 1M) during the period of treatment. The results showed that the native isolated bacteria have high activity in bindings the soil particles together. The results of unconfined compressive strength tests showed that using MICP helps increase the undrained shear strength of soil by (3-5 times) for C11 types of native isolates, but the D11 was (1.5-2 times) because two types have different activity. This study's main finding is using the native urease-producing bacteria isolated from Iraqi soil in the MICP technique for the biocementation of soil, which is considered one of the sustainable techniques in the construction industry.

Influence of Microbial Consortium in the Production of China Aster and Gaillardia Seedlings

China aster and gaillardia are flowering plants with high economic importance in floriculture. In the present investigation, response of China aster and gaillardia seedlings to inoculation with the arbuscular mycorrhizal fungus Funneliformis mosseae + the plant growth-promoting rhizobacterium Bacillus sonorensis was studied by growing in multipots (pro trays). The germination percentage and plant growth parameters: length of shoots, roots and whole seedlings, stem diameter, biovolume index, plant strength, vigor index, dry weight and nutrient uptake, were analyzed 60 days after sowing. The microbial parameters, mycorrhizal root colonization and spore count, and the population of B. sonorensis in the substrate were also determined. The results brought out that growth of inoculated seedlings was significantly improved as compared to uninoculated seedlings. Based on the plant growth and microbial parameters studied, it was concluded that inoculating the substrate in pro trays with the microbial consortium results in producing vigorously growing seedlings.

Optimization of Some Nutritional Conditions and α- Ketoglutaric Acid Concentration as PGA Precursor for Maximizing PGA Production from Bacillus sp. 42 and Bacillus sonorensis 44

Poly gamma glutamic acid is a biodegradable, water soluble and non-toxic edible biopolymer, PGA has nylon back bone similar structure and expressed as bio-nylon. Various bacterial strains produced PGA on of them Bacillus sp. such as B. subtilis, B. lichanformans and B. sonorensis. Polymer yield was affected with medium composition as nitrogen and carbon sources. The current experimental was carried out using shake flask technique for PGA production during 72 of fermentation. The highest biomass was achieved at glycerol media and glucose media for PGA yield and productivity being 2.31, 9.65 gl-1 and 0.134 gl-1h-1, respectively of B. sonorensis 44. Of nitrogen source, organic source (yeast extract) was higher PGA yield and productivity than inorganic sources (NH4NO3) which reduced PGA yield about 28.7 and 36.02% of Bacillus sp. 42 and B. sonorensis 44, respectively. Production media supple- mented with 0.5 and 0.75 gl-1 α-keto-glutaric acid increased PGA yield about 1.24fold for both Bacillus strains. Osmotic pressure of 2.55 MPa (3% NaCl) enhanced PGA yield about 1.18 and 1.24fold of Bacillus sp. 42 and B. sonorensis 44, respectively. Furthermore, the highest PGA was received using medium containing glucose and yeast extract (as C and N2 sources). α-keto-glutaric acid and osmotic potential has an induction effect for polymer accumulation.

Microbial Consortium Promotes Growth of Zinnia and Balsam Seedlings Raised in pro trays

Zinnia and Balsam are flowering plants with high economic importance in floriculture. Inoculation of the planting medium with a beneficial microbial consortium is an innovative approach to produce quality and healthy seedlings in floriculture. In the present study the influence of a microbial consortium of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae and a plant growth promoting rhizobacterium (PGPR) Bacillus sonorensis on flowering plants Zinnia and Balsam in pro-trays under poly house conditions was investigated. Estimation of various plant growth parameters such as plant height, stem diameter, bio-volume index, vigour index, plant strength, fresh weight, dry weight and nutrient uptake was carried out to analyse the ability of the consortium to improve seedling growth. Microbial parameters such as mycorrhizal root colonization and spore count, and population of PGPR in substrate was also studied. The results suggested that inoculating the substrate in pro trays before sowing the seeds with the consortium increased plant growth significantly compared to the uninoculated plants.

Isolation, Identification and Evaluation of Egyptian Bacillus sp. Isolates for Producing Poly-γ-glutamic Acid

Poly-γ-glutamic acid (γ-PGA) is a non-toxic, biodegradable, and water-soluble polymer secreted from different microbes. We isolated forty-nine Bacillus spp. isolates generating PGA from the soil of different Egyptian regions. A total of 18% of these isolates were found to highly produce PGA in the range of 5- 8 gl-l. Two of them, B44 and B42, were identified by the16SrRNA DNA sequence, and they shared 81% of similarity. The most similar DNA sequences to B44-16SrRNA were Bacillus sp. (FJ607057.1) and Bacillus sonorensis (KP236346.1) matching 99% and 94% of similarity, respectively. However, B42-16SrRNA was similar 99% to several Bacillus species. The tree-building algorithm MEGA-X constructed the phylogenetic tree of 16SrRNA DNA sequences for Bacillus 44 and Bacillus 42 strains along with other similar Bacillus species revealing the distance between them. We also boosted the PGA production of both strains. Bacillus 44 strain revealed the highest accumulation level of PGA at 35°C and 72 h of incubation using medium M with inoculum size and agitation speed 3% and 250 rpm, respectively. Both strains secreted the PGA biopolymer with a molecular mass of 55 kDa. This investigation is an attempt of boosting promising Egyptian Bacillus sp. isolates for PGA production that may be a seed for industrial production.