Bioprocess and Biosystems Engineering

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.

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.

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.

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.

Benzyl propionate synthesis by fed-batch esterification using commercial immobilized and lyophilized Cal B lipase Abstract In this work, a fed-batch approach was adopted to overcome propionic acid lipase inactivation effects in the benzyl propionate direct esterification mediated by lipases. The ester synthesis was performed using commercial immobilized (Novozym 435) and lyophilized form Candida antarctica fraction B lipase (Cal B) as biocatalysts of the esterification between benzyl alcohol and propionic acid in a solvent-free system. The reaction involved the propionic acid-controlled addition during the first 5 h ensuring an excess of alcohol to dilute the media. The biocatalyst Novozym 435 showed a good performance in the first cycle of the fed-batch esterification, ensuring 90 and 99% of conversion at substrates molar ratio of 1:1 and 1:5 (acid:alcohol), respectively. However, the enzyme lost the activity and the conversions were sharply reduced at the second cycle. A novel qualitative protein content analysis by optical microscopy showed that the lipase was desorbed from the support after the esterification, and this behavior was strongly related to the presence of propionic acid in the reaction medium. The lyophilized Cal B was also tested as biocatalyst of the benzyl propionate esterification and showed a similar performance (related to the Novozym 435) in ester conversion and initial reaction rates for all substrates molar ratios tested. Since the substrates affected the performance of the Novozym 435, the lyophilized Cal B is the most suitable catalyst to the benzyl propionate esterification with conversions above 90%, considering a the fed-batch approach in a solvent-free system.

Biogas production: evaluation of the influence of K 2 FeO 4 pretreatment of maple leaves ( Acer platanoides ) on microbial consortia composition Abstract The potential of K2FeO4 as a pretreatment agent of a lignocellulosic material was examined on leaves of Acer platanodides as the sole substrate for biogas production by anaerobic digestion carried out through modelling laboratory-scaled semi-continuous reactors differing in loading rates and substrate (pretreated and untreated leaves). The quality of bioagas produced by K2FeO4-pretreated leaves was significantly better in terms of higher methane content and lower content of H2S. K2FeO4 had no crucial influence on growth inhibition of biogas-producing bacteria, which were analysed by comprehensive culture-independent methods utilising high-throughput sequencing of specific genes [bacterial and archaeal 16S rRNA, formyltetrahydrofolate synthetase gene (fhs), methyl-coenzyme M reductase α subunit gene (mcrA) and fungal internal transcribed spacers (ITS)]. The higher amount of CH4 in biogas utilising pretreated leaves as substrate could be caused by a shift to acetoclastic methanogenesis pathway, which was indicated by the higher amount of homoacetogenic bacteria and acetotrophic methanogens detected in those reactors.

Evaluation of predominant factor for shortcut biological nitrogen removal in sequencing batch reactor at ambient temperature Abstract The shortcut biological nitrogen removal (SBNR) process requires less aeration and external carbon due to the oxidization of ammonia into nitrite and its direct denitrification to nitrogen gas during the biological nitrogen removal process. However, this process produces a poor effluent containing NH4+, since the system has to maintain a high free ammonia (FA, NH3) concentration. To overcome this drawback, in this study, the solid retention time (SRT) and the dissolved oxygen (DO) concentration were controlled to achieve both a high ammonia removal rate and nitrite accumulation in the sequencing batch reactor (SBR) process, which can remove nitrogen from wastewater to the desired concentration and provide high free ammonia inhibition and continuous shock loading. When sufficient DO was supplied, nitrite did not accumulate with a 20-day SRT, but the wash-out of nitrite oxidizers in a shorter SRT resulted in a high nitrite accumulation. When DO acted as a limitation, nitrite accumulated at all SRTs. This indicates that nitrite accumulation is more highly influenced by SRT and DO concentration than by FA inhibition. Also, as nitrite accumulated over a 10-day SRT regardless of DO concentration, the accumulation was more highly influenced by SRT than by DO concentration.

Impact of phenol on the performance, kinetics, microbial communities and functional genes of an autotrophic denitrification system Abstract Nitrate and phenol often co-occur in wastewater because of the complex industrial and agricultural processes, while the impacts of phenol on autotrophic denitrification remain unclear. Here, a sulfur and hydrogen-oxidizing autotrophic denitrification reactor was established, and the effects of different concentrations of phenol on the nitrate removal performance, kinetics, microbial communities, and functional genes were investigated. Increasing concentrations of phenol significantly decreased the denitrification efficiency in the reactor. The kinetic data indicate the limitation of nitrate diffusion may be one of reasons. Increasing phenol concentrations declined the activities of nitrate and nitrite reductases and induced the production of reactive oxygen species (ROS) and the release of lactate dehydrogenase (LDH), suggesting potential toxicity to the denitrifying consortium. Denitrifying gene nirK was most sensitive to phenol stresses in the reactor. In addition, Thauera was the predominant genus in system with and without phenol, Bacillus was enriched under high phenol concentrations.

Effects of sugarcane bagasse hydrolysate (SCBH) on cell growth and fatty acid accumulation of heterotrophic Chlorella protothecoides Abstract Microalgal lipid production by Chlorella protothecoides using sugarcane bagasse hydrolysate was investigated in this study. First, maximum glucose and reducing sugar concentrations of 15.2 and 27.0 g/L were obtained in sugarcane bagasse hydrolysate (SCBH), and the effects of different percentages of glucose and xylose on algal cultivation were investigated. Afterwards, SCBH was used as a carbon source for the cultivation of C. protothecoides and higher biomass concentration of 10.7 g/L was achieved. Additionally, a large amount of fatty acids, accounting up to 16.8% of dry weight, were accumulated in C. protothecoides in the nitrogen-limited (0.1–1 mmol/L) culture. Although SCBH inhibited fatty acid accumulation to a certain degree and the inhibition was aggravated by nitrogen starvation, SCBH favored microalgal cell growth and fatty acid production. The present study is of significance for the integration of cost-effective feedstocks production for biodiesel with low-cost SCBH as well as environmentally friendly disposal of lignocellulosic wastes.