Biotechnological potential of Chlorella sp. and Scenedesmus sp. microalgae to endure high CO 2 and methane concentrations from biogas Abstract Biogas, a gaseous effluent from the anaerobic digestion of organic waste, is considered an important source of energy, since it has a composition mainly of methane (CH4; 55–75%) and CO2 (20–60%). Today, CO2 from biogas is an excellent carbon source to induce high microalgal biomass production; however, each microalga strain can have different optimal CO2 concentrations for maximizing their bio-refinery capacity as well as different ability to endure stressful conditions of industrial effluents. This study assessed the bio-refinery capacity of Chlorella sp. and Scenedesmus sp., native of Lago de Chapala, Mexico, from biogas, as well as the effect of high CO2 and methane concentrations on the physiological performance to grow, capture CO2 and biochemical composition of both microalgae cultured under different biogas compositions. The results show that both microalgae have the biotechnological potential to endure biogas compositions of 25% CO2–75% CH4. Under this condition, the biomass production attained by Chlorella sp. and Scenedesmus sp. was 1.77 ± 0.32 and 2.25 ± 0.20 g L−1, respectively, with a biochemical composition mainly of carbohydrates and proteins. Overall, this study demonstrates that both microalgae have the ability to endure the stressful biogas composition without affecting their physiological capacity to capture CO2 and biosynthesize high-value metabolites. Moreover, it is worth highlighting the importance of screening wild-type microalgae from local ecosystems to determine their physiological capacity for each biotechnological application.

Alginate–pectin co-encapsulation of dextransucrase and dextranase for oligosaccharide production from sucrose feedstocks Abstract The genes for dextransucrase and dextranase were cloned from the genomic regions of Leuconostoc mesenteroides MTCC 10508 and Streptococcus mutans MTCC 497, respectively. Heterologous expression of genes was performed in Escherichia coli. The purified enzyme fractions were entrapped in the alginate–pectin beads. A high immobilization yield of dextransucrase (~ 96%), and dextranase (~ 85%) was achieved. Alginate–pectin immobilization did not affect the optimum temperature and pH of the enzymes; rather, the thermal tolerance and storage stability of the enzymes was improved. The repetitive batch experiments suggested substantially good operational stability of the co-immobilized enzyme system. The synergistic catalytic reactions of alginate–pectin co-entrapped enzyme system were able to produce 7–10 g L−1 oligosaccharides of a high degree of polymerization (DP 3–9) from sucrose (~ 20 g L−1) containing feedstocks, e.g., table sugar and cane molasses. The alginate–pectin-based co-immobilized enzyme system is a useful catalytic tool to bioprocess the agro-industrial bio-resource for the production of prebiotic biomolecules.

Immobilized enzyme on pulp fiber through layer-by-layer technique using cationic polyacrylamide for whitewater treatment from papermaking Abstract Anionic pectic substances in whitewater from papermaking are detrimental to machine operation and product quality. Pectinase was immobilized on pulp fiber using cationic polyacrylamide with layer-by-layer method to obtain bound enzyme with tunable activity and good performance for wastewater treatment. It was revealed that high charge density and low molecular weight for cationic polyacrylamide were advantageous for enzymatic activity. During the layer-by-layer adsorption process, the enzymatic activity of the immobilized enzyme increased nearly linearly with the layer number from 983 to 3074 U/g until the fourth layer. The stability of the four-layer immobilized enzyme was improved. The multilayer immobilized enzyme exhibited good reusability and storage stability compared with monolayer enzyme. At dosage of 10 U/mL, the cationic demand of the whitewater samples was reduced by 15% using four-layer immobilized enzyme. The results indicated a potential route to prepare immobilized enzyme with good performance for wastewater treatment in papermaking industry.

Mixotrophy in Synechocystis sp. for the treatment of wastewater with high nutrient content: effect of CO 2 and light Abstract Synechocystis sp. has remarkable mixotrophic capabilities, as well as an efficient exploitation of nitrogen and phosphorus, that may be applied in wastewater treatment based on cyanobacteria. To better investigate the exploitation of algal mixotrophy in bioremediation, this species was used in axenic respirometric tests to ascertain the effect of high light and non limiting CO2 supply on the overall regulation of mixotrophy, resulting in an inhibition of the exploitation of organic carbon. The same species was then cultured in real, unsterilized effluent obtained from the acidogenic fermentation of sludge, which contains a high concentration of nutrients (approximately 600, 90 and 6000 mg L−1 of N, P and COD, respectively) and it is often inhibiting for many microalgal species. On the contrary, Synechocystis sp., showed a remarkable growth and a removal up to 96% of phosphorus, 66% of nitrogen and of 68% of COD in such a complex waste stream.

Improving poly-(γ-glutamic acid) production from a glutamic acid-independent strain from inulin substrate by consolidated bioprocessing Abstract To excavate the application of Jerusalem artichoke on poly(γ-glutamic acid) (γ-PGA) production, a γ-PGA producing strain Bacillus amyloliquefaciens NX-2S154 was obtained through atmospheric and room temperature plasma mutagenesis, which produced 14.83 ± 0.31 g/L of γ-PGA in batch fermentation with raw inulin extract. Simultaneous saccharification and fermentation (SSF) by adding commercial inulinase were further investigated for γ-PGA fermentation. Results showed SSF could eliminate the ineffective utilization of inulin while avoiding inhibition effect of high concentration substrate, which made γ-PGA concentration reach 18.54 ± 0.39 g/L with the process being shortened by 17%. Finally, an immobilized column for reducing inulinase cost was introduced to γ-PGA production. Repeated batch cultures showed the novel bioreactor exhibited higher stability and simplicity and gave average γ-PGA concentration and productivity of 19.40 ± 0.37 g/L and 0.27 ± 0.008 g/L/h, respectively. This work proposes a productive method for efficient γ-PGA production using Jerusalem artichoke feedstock.

Enhanced production of triacylglycerols and polyunsaturated fatty acids in novel acid-tolerant mutants of the green microalga Chlorella saccharophila Abstract In this study, the microalga Chlorella saccharophila was subjected to ultraviolet (UV) mutagenesis, and mutant screening was conducted based on acidity tolerance to generate mutants with increased triacylglycerol (TAG) and polyunsaturated fatty acid (PUFA) contents. Two improved mutant strains (M1 and M5) were generated. M1 and M5 accumulated 27.2% and 27.4% more TAG, respectively, and showed stronger fluorescence intensity than the wild-type (WT) strain when the cells of these mutants were stained with the lipophilic Nile Red stain. In the M1 mutant, 50.5% of the fatty acid methyl esters (FAMEs) were saturated (C16:0 and C18:0) and 25.27% were monounsaturated (C18:1) fatty acids which are suitable for biofuels production. In the M5 mutant, 65.19% of the total FAMEs were nutritional PUFAs (C16:2, C18:2, and C18:3), while these FAMEs were not detected in the WT. These results demonstrated that UV mutagenesis coupled to an acid pH screening strategy represents a valuable and fast platform to generate mutants of C. saccharophila with improved TAG and PUFA contents for biofuels and nutraceutical applications, respectively.

The impact of technical failures during cultivation of an inclusion body process Abstract In biotechnological processes, technical failures in the upstream process often lead to batch loss. It is of great interest to investigate the empirical impact of technical failures to understand and mitigate their impact accurately and reduce economic damage. We investigated the impact in the upstream and downstream of a recombinant antibody fragment inclusion body production process chain to provide integrated empirical data and knowledge. First, we provided a reproducible process chain that yielded high inclusion body content, high specific product titer, and a refolding yield of 30%. The inclusion body downstream proved to be of high reproducibility. Through the intended introduction of technical failures, we were not only able to shed more light on the empirical responses in the upstream and downstream, but also on process-boosting parameters that would have been neglected. Herein, a short increase in temperature during the cultivation clearly increased the refolding yield.

Comparison of downstream processing methods in purification of highly active laccase Abstract Laccases have received the attention of researchers in the last few decades due to their ability to degrade phenolic and lignin-related compounds. This study aimed at obtaining the highest possible laccase activity and evaluating the methods of its purification. The crude laccase from bioreactor cultivation of Cerrena unicolor fungus was purified using ultrafiltration, aqueous two-phase extraction (ATPE) and foam fractionation (FF), which allowed for the assessment of these three downstream processing (DSP) methods. The repeated fed-batch cultivation mode applied for the enzyme production resulted in a high laccase specific activity in fermentation broth of 204.1 U/mg. The use of a specially constructed spin filter inside the bioreactor enabled the integration of enzyme biosynthesis and biomass filtration in one apparatus. Other methods of laccase concentration and purification, namely ATPE and FF, proved to be useful for laccase separation; however, the efficiency of FF was rather low (recovery yield of 24.9% and purification fold of 1.4). Surprisingly, the recovery yield after ATPE in a PEG 6000-phosphate system in salt phase was higher (97.4%) than after two-step ultrafiltration (73.7%). Furthermore, it was demonstrated that a simple, two-step purification procedure resulted in separation of two laccase isoforms with specific activity of 2349 and 3374 U/mg. All in all, a compact integrated system for the production, concentration and separation of fungal laccases was proposed.

Comparative efficacy of machine-learning models in prediction of reducing uncertainties in biosurfactant production Abstract An accurate and reliable forecast of biosurfactant production with minimum error is useful in any bioprocess engineering. Bacterial isolate FKOD36 capable of producing biosurfactant was isolated in this study and pre-inoculums was prepared from the agar slants in a small test tube and incubated at 30 °C for 24 h at 120 rpm. Due to inherent non-linearity characteristics of the data set in a bioprocess, conventional modeling techniques are not adequate for predicting biosurfactant production in a microbiological process. The main contribution of the study was to compare two soft-computing models, i.e., support vector regression (SVR) and support vector regression coupled with firefly algorithm to evaluate the best performance of the two mentioned models. Based on the results it was noted that support vector regression coupled with firefly algorithm performs better compared to the simple SVR.

Biotransformation of phenolic compounds by Bacillus aryabhattai Abstract Phenolic compounds could pose environmental problems if they are in excess, although they could be a renewable resource of substances with industrial interest. The novel strain Bacillus aryabhattai BA03 is able to produce high-added value metabolites from different phenolic compounds such as vanillin, 4-vinylguaiacol and 4-vinylphenol while inducing ligninolytic enzymes such as laccases (Lac) and lignin peroxidases (LiP). In comparison with the medium without inducers, the presence of 500 mg/L caffeic acid improved 9.1-fold times the expression of Lac (0.118 ± 0.004 U/mL) and 5.8-fold times the expression of LiP (2.300 ± 0.053 U/mL), just as these processes exhibited high global rates of biotransformation. When isoeugenol, ferulic acid or p-coumaric acid are in the media, the strain removed more than 90% of these compounds, secreting vanillin, 4-vinylguaiacol or 4-vinylphenol. Bacillus aryabhattai proved to be an appropriate tool for the removal of several phenolic compounds and the production of more valuable products.