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This study evaluated the bioproduction of 1,3-propanediol by Lactobacillus diolivorans in the medium based on agro-industrial residues and vegetal biomass substituting the MRS medium components. It was performed on a set of acid treatments and batch fermentations assays with crude glycerol (TCG) from biodiesel production, corn steep liquor (CSL), and cactus cladode hydrolyzate (CCH). Firstly, it was carried out on batch fermentation with different pure glycerol concentrations in MRS medium which was carried out, and the best condition achieved 4.66 g/L and 0.61 g/g of 1,3-PDO production and yield, respectively. Then, the TCG was evaluated, and a discrete increase of 1,3-PDO was observed. The replacement of the MRS medium nutrients by CLS was assessed, at different concentrations, for bacteria growth, and 5% of CLS reproduced the same biomass formation compared to the bacteria growth in MRS medium. It was also added cactus cladode hydrolyzate as the only sugar source, which showed a 1,3-PDO production close to the medium with pure glucose. Finally, a B-complex vitamin was added to the batch fermentation medium composed of TCG, CLS, and CCH, replacing all the costly MRS components. In this medium, the production of 1,3-propanediol was 6.57 g/L with a yield of 0.75 g/g. It means an increment of 29% and 19%, respectively, compared to MRS medium. Therefore, the combination of treated crude glycerol, corn steep liquor, and cactus cladode hydrolyzate has excellent potential for 1,3-PDO production by L. diolivorans.

Economically viable alternatives for utilizing municipal solid waste are still a major challenge for society, especially in less developed countries. A potential pathway is using the organic fraction of municipal solid waste (OFMSW) to produce energy, biofuels, organic fertilizers, and value-added chemical compounds. We evaluated an integrated biorefinery structure for the treatment of used cooking oil, pruning biomass, and organic and food residues to produce biodiesel, biogas, organic compost, 1,3-propanediol, and electrical energy at the campus of the Federal University of Pernambuco, which was considered a case study to represent a small city of Northeastern Brazil. A pilot transesterification plant, a biodigestion unit, and a compost unit were installed to process 3.3 tons daily of OFMSW produced. Additionally, research was carried out to produce 1,3-propanediol on a laboratory scale from residual glycerol. The quality of the biodiesel generated from the used cooking oil met national technical standards and the conversion of residual oil into biodiesel reached 93%. The average biogas production was 0.584 ± 0.176 Nm3 kgVS−1, with an average methane production of 50% generating up to 44 MWh of electricity per year. The organic compost produced met the quality requirements of organic fertilizers, such as maturation and nutrient contents. Glycerol treatment increased the yield of 1,3-propanediol production. Our findings demonstrate that the integrated biorefinery will lead to a reduction of US$ 80,000 in the costs of OFMSW management. More importantly, this approach generates incentives for circular economy initiatives in small municipalities in Brazil and other less developed countries.

The most important alkaline proteases from the commercial standpoint are produced by bacteria of the genus Bacillus and used mainly in the formulation of detergents. The aim of the present study was to evaluate the production, partial purification, and characteristics of alkaline protease obtained by Bacillus firmus var. arosia NCIB 10557 in fed-batch fermentation with constant feeding profile and carbon source restriction. Firstly, it was carried out on batch fermentation and after 6.5 h of fermentation, glucose became limiting, and then the fed-batch was started with a flow rate of 0.0802 mL/min. Maximum activity (998.1 U/mL) was reached after 10.5 h of fed-batch, with a subsequent 60.91 % drop in activity after two hours. The purification steps resulted in a 1.65-fold increase in the value of the specific activity. The protease showed optimum activity at 37°C and pH 9 and residual activity above 80 % at pH 11 and 12. Residual activity was greater than 70 % at temperatures ranging from 30 to 70 °C and 90 % of this activity was maintained for 30 minutes at 70 °C until the occurrence of complete inactivation. Enzyme activity was estimated using SDS. The organic solvents Triton X-100, Tween-20, EDTA and β-mercaptoethanol and the ions Zn2+, Fe2+, Cu2+ and Ni2+ partially inhibited the activity of the protease. Ca2+, Mn2+ and Mg2+ had no stimulating action on the enzyme.