Theoneste Ndikubwimana | Xiamen University (original) (raw)

Papers by Theoneste Ndikubwimana

De Gruyter eBooks, Sep 17, 2023

Biochemical Engineering Journal, 2015

Poly-␥-glutamic acid (␥-PGA) broth was found to be a good bioflocculant of microalgae. However, t... more Poly-␥-glutamic acid (␥-PGA) broth was found to be a good bioflocculant of microalgae. However, the mechanism governing this bioflocculation process is not fully understood. In this study, Zeta potential measurement, microscopy examination and classical DLVO theory (named after Derjaguin, Landau, Verwey and Overbeek) analysis were used to explore the flocculability of microalgae induced by bacterial ␥-PGA broth bioflocculant. Microalgae flocculation could be significantly improved by modifying ionic strength of the microalgae suspension, lowering pH value and bioflocculant addition due to the stronger attraction interactions between microalgal cells. In the present study, both the pH reduction with the bioflocculant induced better the flocculation process compared to the modification of ionic strength of the microalgae suspension in the presence of the bioflocculant. The DLVO theory indicated that when the bioflocculant was introduced, the total interaction energy decreased sharply, resulting in higher flocculation efficiency (>96 %) at a separation distance of 5 nm and shorter settling time (from 2 h to 10 min) compared with that obtained only by reducing the initial pH. The microalgae interaction energy was found to be dependent on the Zeta potential. This study provided a detailed interpretation of conceivable mechanism of microalgae bioflocculation by ␥-PGA broth.

Algal Research, 2014

The small particulate size of microalgae cells and the extremely dilute concentrations of microal... more The small particulate size of microalgae cells and the extremely dilute concentrations of microalgae cultures continue to be major challenges to effective harvesting. In an attempt to find a cost-effective and environmentally friendly harvesting technique, the bioflocculant poly (γ-glutamic acid) (γ-PGA) produced by Bacillus licheniformis CGMCC 2876 was used to concentrate freshwater microalgae Desmodesmus sp. F51. Experimental results showed that the flocculation efficiency was dependent on the initial culture pH. The flocculation efficiency increased from 43.8 ± 1.6% to 98.2 ± 0.1% when the initial culture pH was changed from~7.2, as the original culture pH, to 3. With the optimum operating parameters of bioflocculant dosage of 2.5 mL/L, flash mixing rate of 150 rpm for 1 min, and slow mixing rate of 80 rpm for 2 min, a flocculation efficiency of 99% was achieved. Microscopic photos of the harvested microalgae cells showed no cell damage and hence no premature release of intracellular contents during the process. The bioflocculation process is easy to operate, cost-efficient, environmentally friendly and as effective as chemical flocculation processes applied industrially. The γ-PGA bioflocculant produced by B. licheniformis CGMCC 2876 demonstrated high performance for optimal microalgae recovery and can be applied in commercial-scale microalgae harvesting.

随着世界对食品、饲料、生物燃料和化工产品需求的日益增长，微藻成为了被广泛接受的最具有前景的原材料之一。然而，微藻细胞个体微小，培养密度低，藻体难以高效收集，影响了微藻产品的生产和商业化。本研究从... more 随着世界对食品、饲料、生物燃料和化工产品需求的日益增长，微藻成为了被广泛接受的最具有前景的原材料之一。然而，微藻细胞个体微小，培养密度低，藻体难以高效收集，影响了微藻产品的生产和商业化。本研究从经济和环保的角度出发，建立了一种使用生物絮凝剂絮凝收集藻体的方法。方法使用地衣芽孢杆菌CGMCC2876生产的聚谷氨酸作为生物絮凝剂，絮凝并收集淡水藻体，同时使用zeta电位测定和DLVO经典理论对絮凝过程进行了分析研究，并对絮凝操作的可放大性和原位操作的可行性进行了实验评估。此外，本研究对所收集微藻的生化组成进行了测定，分析了其作为生物燃料的可行性。实验结果表明，微藻的絮凝收率取决于藻液的初始pH值。...In respect to compensate the unremittingly increasing global demand for food, feed, biofuels, and chemicals production, microalgae has been widely regarded as one of the most promising raw materials. However, the small particulate size of microalgae cells and the extremely dilute concentrations of microalgae cultures continue to be the major challenges to effective microalgae harvesting, thus hind...学位：工学博士院系专业：化学化工学院_化学工程学号：2062013015440

Microalgae are widely regarded as one of the most promising and sustainable raw materials, especi... more Microalgae are widely regarded as one of the most promising and sustainable raw materials, especially for biofuels. However, the full exploitation of microalgae resources is significantly hindered through the lack of the eco-friendly microalgae harvesting due to the microalgae cultures that are incredibly diluted, as well as the small particulate size of microalgae cells, thus hindering the production and commercialization of microalgae-based products. This chapter provides a brief summarization of current technologies of algal biomass harvesting and dewatering, components extraction, and products conversion. These technologies are aimed to reduce the cost of downstream processes and promote environmental protection. Also, common microalgae-derived products including biodiesel, hydrogen, biogas, syngas, pigments, and fatty acids are described.

Additional file 1: Figure S1. Glucose and BSA standard curves. The standard curve describes gluco... more Additional file 1: Figure S1. Glucose and BSA standard curves. The standard curve describes glucose and BSA standard curves, (a) for total carbohydrates and (b) for total proteins quantification, respectively.

Global issues such as environmental degradation, hunger and malnutrition, poverty, antibiotic res... more Global issues such as environmental degradation, hunger and malnutrition, poverty, antibiotic resistance, chronic diseases, depletion of fossil fuels and other issues associated with their utilization, among others, are burdening the global population’s quality of life. Algal resources are well-positioned, prominent, and sustainable resources for providing some solutions to global challenges such as malnutrition, antibiotic resistance, and environmental degradation. Algal resources play a dual role, which is feedstocks with a broad range of applications (including healthy foods, food supplements, feeds, and bio-energy) coupled with environmental phycoremediation. This review article is amained to elucidate the potentials of algal resources from the current scientific literature and to highlight their inputs in solving current pressing global challenges. The approaches and strategies that can contribute to the achievement of sustainable development through the utilization of algal re...

Bioresource technology, 2018

Arthrospira (Spirulina) platensis is known to have high-quality proteins content and phycocyanin ... more Arthrospira (Spirulina) platensis is known to have high-quality proteins content and phycocyanin as one of the major pigment constituents of the cells, and the most challenging problem associated with phycocyanin production in Arthrospira is to optimize its intracellular accumulation. The present study evaluated the metabolic stress conditions (by nutrient enrichment) of Arthrospira platensis FACHB-314 for boosting biomass growth and high content phycocyanin accumulation. Experimental results showed that 5 mM sodium glutamate and 7.5 mM succinic acid could enhance biomass yield as well as phycocyanin accumulation compared with that of the control groups. The present study demonstrates that the biomass growth and phycocyanin accumulation were significantly enhanced in fed-batch cultivation of Arthrospira platensis by applying the substrates as metabolic stress agents combined with nitrate feeding strategy. cobA/hemD, hemG and ho genes presented the over-expression level with adding s...

Biochemical Engineering Journal, 2016

Abstract Microalgae are considered as a great potential for reliable and sustainable feedstock fo... more Abstract Microalgae are considered as a great potential for reliable and sustainable feedstock for the production of biofuels and biochemically active compounds such as phycobiliproteins. Phycobiliproteins are a group of colored proteins present commonly not only in cyanobacteria (blue–green algae) but also in red algae, cryptomonads, etc. They are extensively commercially used in foods, cosmetics, biotechnology, pharmacology and medicine. Phycobiliproteins have high potential pharmaceutical and biological properties but their application is confronted with two major obstacles: (i) the upstream and downstream processes still have some hindrances such as selection of suitable microalgae strains, bioreactor design, culture conditions, etc.; (ii) the purification of phycobiliproteins from microalgae is still low. Biosynthesis of higher purity phycobiliproteins from microalgae is a multiple concomitant steps for which the main criteria and factors were discussed in this paper. This review highlights an overview on the phycobiliproteins application fields such as pharmaceutical, medicine, biological and diagnostic reagents, etc., and meanwhile provides an insight for further research in development, production, and application of phycobiliproteins.

Journal of Applied Phycology, 2017

Phycocyanin, a blue pigment, is a type of phycobiliproteins. Because of its various potential pro... more Phycocyanin, a blue pigment, is a type of phycobiliproteins. Because of its various potential properties, phycocyanin is applied to various fields, such as nutraceutical, pharmaceutical, medicine, cosmetics, and biotechnological research. The cost and application of phycocyanin are highly dependent on its purity index. In this study, ammonium chloride is presented as a novel, effective, and inexpensive salt for phycocyanin extraction. Compared with sodium phosphate, which is commonly used during phycocyanin extraction process, ammonium chloride solution efficiently extracted phycocyanin with high purity from Arthrospira platensis FACHB-314. In addition, ammonium phosphate solution is also presented as an alternative precipitation agent in phycocyanin purification that may replace the widely used ammonium sulfate. Statistical analysis shows that there is no significant difference in phycocyanin concentration between crude extracts (overall mean of 0.208 and 0.215 for extraction using sodium phosphate and ammonium chloride, respectively). However, the difference in phycocyanin purity ratio (A620/A280) between these two extractions is significant (overall mean of 0.742 and 1.428 for extraction using sodium phosphate and ammonium chloride, respectively). With ammonium chloride, the purity indexes of phycocyanin are 1.5 and 2.81 after the optimum extraction step, and precipitation used as the primary purification step, respectively. The present study describes a novel purification method to achieve phycocyanin with analytical grade without multiple purification steps.

Biotechnology Journal, 2016

Microalgal biomass as renewable energy source is believed to be of great potential for reliable a... more Microalgal biomass as renewable energy source is believed to be of great potential for reliable and sustainable biofuels production. However, microalgal biomass production is pinned by harvesting and dewatering stage thus hindering the developing and growing microalgae biotechnology industries. Flotation technology applied in mineral industry could be potentially applied in microalgae harvesting and dewatering, however substantial knowledge on different flotation units is essential. This paper presents an overview on different flotation units as promising cost-effective technologies for microalgae harvesting thus bestowing for further research in development and commercialization of microalgae based biofuels. Dispersed air flotation was found to be less energy consuming. Moreover, Jameson cell flotation and dispersed ozone flotation are believed to be energy efficient microalgae flotation approaches. Microalgae harvesting and dewatering by flotation is still at embryonic stage, therefore extended studies with the focus on life cycle assessment, sustainability of the flotation unit, optimization of the operating parameters using different algal species is imperative. Though there are a number of challenges in microalgae harvesting and dewatering, with well designed and developed cultivation, harvesting/dewatering, extraction and conversion technologies, progressively, microalgae technology will be of great potential for biological carbon sequestration, biofuels and biochemicals production.

Biochemical Engineering Journal

Biotechnology for Biofuels, 2016

Background: Nowadays, bioflocculation is considered as a potential technology that could be able ... more Background: Nowadays, bioflocculation is considered as a potential technology that could be able to alleviate microalgae dewatering cost regarded as the cornerstone hindrance of their full-scale application. However, most bioflocculation studies reported are laboratory scales. This study examined a pilot-scale and in situ flocculation of freshwater microalgae Desmodesmus brasiliensis by microbial bioflocculant. Biochemical composition of microalgal biomass was analyzed to evaluate the applicability of bioflocculation for microalgae-based biofuel production. Results: The flocculation efficiency >98 % was achieved at both pilot-scale and in situ treatment. Bioflocculation is simple, effective, economic, and environmentally friendly. Even though total proteins recovered from biomass harvested by centrifugation and that harvested by bioflocculation were significantly different, there was no significant difference in total carbohydrates and total lipids recovered from either biomass harvested by centrifugation or biomass harvested by bioflocculation. Conclusion: The results herein presented, doubtlessly demonstrated that the γ-PGA bioflocculant produced by Bacillus licheniformis CGMCC 2876 is applicable for commercial-scale microalgae harvesting. In addition, bioflocculation process cost could greatly be reduced by in situ operation as no investment cost is needed for a separate flocculation tank and mixing device. Furthermore, bioflocculation method developed is a worthy microalgae harvesting method for algal-based biofuel production.

Frontiers in plant science, 2016

Even though microalgal biomass is leading the third generation biofuel research, significant effo... more Even though microalgal biomass is leading the third generation biofuel research, significant effort is required to establish an economically viable commercial-scale microalgal biofuel production system. Whilst a significant amount of work has been reported on large-scale cultivation of microalgae using photo-bioreactors and pond systems, research focus on establishing high performance downstream dewatering operations for large-scale processing under optimal economy is limited. The enormous amount of energy and associated cost required for dewatering large-volume microalgal cultures has been the primary hindrance to the development of the needed biomass quantity for industrial-scale microalgal biofuels production. The extremely dilute nature of large-volume microalgal suspension and the small size of microalgae cells in suspension create a significant processing cost during dewatering and this has raised major concerns towards the economic success of commercial-scale microalgal biofu...

Bioprocess and biosystems engineering, Jan 23, 2016

Polyunsaturated fatty acids (PUFAs) are highly appreciated on their nutritive value for human hea... more Polyunsaturated fatty acids (PUFAs) are highly appreciated on their nutritive value for human health and aquaculture. P. purpureum, one of the red microalgae acknowledged as a promising accumulator of ARA, was chosen as the target algae in the present research. Effects of sodium bicarbonate (0.04-1.2 g/L), temperature (25, 30 and 33 °C) and phosphate (0.00-0.14 g/L) on biomass yield, total fatty acids (TFA) and arachidonic acid (ARA) accumulation were investigated systemically. NaHCO3 dose of 0.8 g/L and moderate temperature of 30 °C were preferred. In addition, TFA and ARA production were significantly enhanced by an appropriate concentration of phosphate, and the highest TFA yield of 666.38 mg/L and ARA yield of 159.74 mg/L were obtained at a phosphate concentration of 0.035 g/L. Interestingly, with phosphate concentration continuing to fall, UFA/TFA and ARA/EPA ratios were increased accordingly, suggesting that phosphate limitation promoted unsaturated fatty acids and arachidonic...