Bioprospecting of exopolysaccharide-producing bacteria from different natural ecosystems for biopolymer synthesis from vinasse

Abstract Background Exopolysaccharides (EPSs) belong to a family of organic thickeners or alternative hydrocolloids of microbial origin. Because the chemical structure offers beneficial bioactive functions, biocompatibility and biodegradability, EPSs are used in the chemical, food, pharmaceutical, cosmetics, and packaging industries as well as in agriculture and medicine. In this study, new bacterial strains were selected on the basis of their ability to synthesize EPS from substrate containing vinasse as a nutrient source to identify the best candidate for bio-based polymer production. Results Among the 99 newly identified bacterial strains isolated from different natural ecosystem, the strain Azotobacter chroococcum 76A was selected as the best biopolymer producer since it synthesized the highest concentration of EPS in all media containing vinasse. The maximum EPS concentration (44.6 ± 0.63 mg/50 mL) was observed at 24 h, corresponding to its sub-stationary growth phase (7 × 108 ± 0.29 CFU/mL). Chemical characterization of the EPS produced showed that carbohydrates representing the principal component, followed by uronic acids and proteins. Interestingly, comparing the IR spectrum of the EPS with alginate by FTIR-ATR analysis revealed an overlap of a peak identified as guluronic acid, a component of alginate. Conclusions The potential biotechnological capacity of A. chroococcum 76A to synthetize biopolymer from vinasse, inexpensive starting materials, represents a possible alternative to expensive disposal of agri-food waste through its transformation into high value-added products

Bio-Based Succinate Production from Arundo donax Hydrolysate with the New Natural Succinic Acid-Producing Strain Basfia succiniciproducens BPP7

n/

Metabolic Profiling and Cold-Starvation Stress Response of Oxygen-Tolerant Lactobacillus gasseri Strains Cultured in Batch Bioreactor

Phenotypic and genotypic evidence indicates that many LAB strains can grow in presence of oxygen and can shift from fermentative to aerobic and/or respiratory metabolism. The aerobic and respiratory growth of several LAB species have been studied, allowing the selection of strains showing improved biomass production, long-term survival, and resistance under oxygen and stress conditions. The aim of this work was to observe the adaptation of two Lactobacillus gasseri strains, described in a previous work, to aerobic (air injection) and respiratory (air injection plus hemin and menaquionone) conditions obtained in a batch bioreactor. One strain showed the higher biomass production and oxygen consumption as well as the lower acidification in respiratory condition. Instead, the other one grew better in aerobic condition, even though the higher resistance to cold-starvation stress was registered in respiratory condition. In silico analysis revealed notable differences between AL3 and AL5 genomes and that of the type strain. This work contributes to understanding the adaptation response of lactobacilli to aerobic and respiratory metabolism. We demonstrated that the supposed activation of respiratory metabolism may provide several modifications to cell physiology. These features may be relevant in some technological and health-promoting applications, including starter and probiotic formulations

Pre-treatment and inoculum affect the microbial community structure and enhance the biogas reactor performance in a pilot-scale biodigestion of municipal solid waste

During anaerobic digestion of municipal solid waste, organic matter is converted to methane, carbon dioxide, and other organic and inorganic compounds through a complex cooperation among different microbial groups with different metabolic activities. Here, culture-dependent and independent approaches provided evidence for examining the relationship between bacterial and archaeal communities and methane production in a pilot-scale anaerobic digestion. The abundance of aerobic and anaerobic functional groups of C and N cycles, such as cellulolytic, pectinolytic, amylolytic and proteolytic bacteria, was high at the beginning of the experiment and was drastically decreased after anaerobic digestion. In contrast, the ammonifiers increased in the biogas producing reactors in a higher pH environment. The methanogenic archaeal genera recovered were Methanobrevibacter, Methanobacterium, Methanoculleus and Methanocorpusculum, thus indicating that methane was formed primarily by the hydrogenotrophic pathway in the reactors. Moreover, the mechanical pretreatment effects, as well as the effect of pelleted manure as inoculum, were considered. The highest methane production was detected in the biodigesters with minced organic waste, thus indicating that pre-treatment of a heterogeneous starting matrix was essential for improving biogas production and stabilizing the process

Enhancing Succinic Acid Production by Sequential Adaptation of Selected <i>Basfia succiniciproducens</i> Strains to <i>Arundo donax</i> Hydrolysate

Promising green technologies that can overcome the challenges associated with the use of fossil fuels require microorganisms that can effectively ferment lignocellulosic hydrolysate for biochemical production with reduced sensitivity to toxic chemicals derived from the pretreatment process. In this study, a sequential adaptation approach was developed to obtain new bacterial lines from Basfia (B.) succiniciproducens strains, which are adapted to inhibitory compounds of the Arundo (A.) donax hydrolysate or those that accumulate during the fermentation process. The early adaptation stages resulted in newly adapted B. succiniciproducens bacterial lines that can tolerate fermentation end-products such as acetic, lactic, and succinic acids, as well as toxic compounds such as furfural and hydroxymethylfurfural. These adapted bacterial lines were further investigated to assess their ability to produce succinic acid in an MHM medium supplemented with a filtrate of A. donax hydrolysate. Batch growth tests on a small laboratory scale showed that bacterial lines 2E and 4D produced 5.80 ± 0.56 g L−1 and 5.81 ± 0.39 g L−1 of succinic acid, respectively, after 24 h of fermentation. Based also on its growth rate, the adapted bacterial line B. succiniciproducens 4D was selected for tests in a lab-scale fermenter, where it was able to synthesize up to 17.24 ± 0.39 g L−1 of succinate (corresponding to YSA/gluc 0.96 ± 0.02 g g−1 and to YSA/(G + X) 0.48 ± 0.01 g g−1) from MHM medium added with A. donax hydrolysate. Experiments showed an increase of ~17% compared to the control strain. The overall results demonstrate the potential of adapted bacterial lines for succinate production from A. donax hydrolysate and the development of improved technologies for bio-based succinic acid production

Bio-based Chemical Production from Arundo donax Feedstock Fermentation using Cosenzaea myxofaciens BPM1

Bio-based organic acids are an eco-friendly alternative to petroleum-derived products. In this work, the production of organic chemicals was investigated for the first time in the Cosenzaea myxofaciens species using hydrolysed lignocellulosic biomass from Arundo donax. The strain C. myxofaciens BPM1, isolated from bovine rumen, was able to produce a high amount of lactic acid, followed by acetic and succinic acids in synthetic substrate in microaerophilic and anaerobic conditions. When hydrolysed lignocellulosic biomass from Arundo donax supplemented with several nitrogen sources was used as substrate in separate hydrolysis and fermentation in anaerobic conditions, a significant increase in organic acids was recovered, reaching values up to 12.13 ± 0.17, 1.68 ± 0.1, and 5.23 ± 0.04 g L-1 of lactate, succinate, and acetate, respectively. Moreover, the strain C. myxofaciens BPM1 was capable of synthesizing a small amount of ethanol, with a resulting concentration ranging from 0.67 ± 0.05 to 1.46 ± 0.03 g L-1. This work shows that the strain C. myxofaciens BPM1 is a potential source of interesting bio-based chemicals for a wide range of industrial applications. In addition, the inexpensive fermentation process using A. donax hydrolysate and corn steep liquor as carbon and nitrogen sources could be suitable for economical and efficient production of succinic acid in industrial processes

The effect of bacterial and archaeal populations on anaerobic process fed with mozzarella cheese whey and buttermilk

Dairy wastes can be conveniently processed and valorized in a biorefinery value chain since they are abundant, zero-cost and all year round available. For a comprehensive knowledge of the microbial species involved in producing biofuels and valuable intermediates from dairy wastes, the changes in bacterial and archaeal population were evaluated when H2, CH4 and chemical intermediates were produced. Batch anaerobic tests were conducted with a mixture of mozzarella cheese whey and buttermilk as organic substrate, inoculated with 1% and 3% w/v industrial animal manure pellets. The archaeal methanogens concentration increased in the test inoculated at 3% (w/v) when H2 and CH4 production occurred, being 1 log higher than that achieved in the test inoculated at 1% (w/v). Many archaeal species, mostly involved in the production of CH4, were identified by sequencing denaturing gradient gel electrophoresis (DGGE) bands. Methanoculleus, Methanocorpusculum and Methanobrevibacter genera were dominant archaea involved in the anaerobic process for bioenergy production from mozzarella cheese whey and buttermilk mixture

Fungal Biodeterioration and Preservation of Miniature Artworks

The study of biodeterioration is an important issue to allow the best conservation and prevent the decay of cultural heritage and artworks. In Naples (Italy), a particular museum (Museodivino) preserves the miniature artworks representing Dante’s Divine Comedy and Nativity scenes, executed with organic-based materials in walnut and clay shells. Since they showed putative signs of biodeterioration, the first aim of this study was to verify the presence of microbial colonization. A culture-dependent approach and molecular biology allowed us to isolate and identify the sole fungal strain Aspergillus NCCD (Nativity and Dante’s Divine Comedy) belonging to the A. sydowii sub-clade. Based on this result, a sustainable and eco-friendly approach was applied to find a method to preserve the miniature artwork by contrasting the growth of the strain NCCD. Several essential oils used as a natural biocide were tested against Aspergillus strain NCCD belonging to the A. sydowii subclade to determine their potential antimicrobial activity. Results revealed that basil, cloves, fennel, and thyme essential oils exerted antifungal activity, although their effect depended also on the concentration used. Moreover, anoxic treatment and the control of the relative humidity were used in the presence of thyme, in vitro, and in vivo assays to define the impact on fungal growth. No fungal development was detected in vivo in the shells treated with thyme essential oil at high relative humidity after 60 days of incubation at 28 °C. These results highlighted that although relative humidity was the major factor affecting the development of the strain Aspergillus NDDC, the application of thyme in an anaerobic environment is essential in contrasting the fungal growth. Identifying the biodeterioration agent allowed us to plan an eco-friendly, non-destructive approach to be successfully used to guarantee the conditions suitable for conserving miniature artwork