Development of continuous cultivation process for oil production through bioconversion of minimally treated waste streams from second‐generation bioethanol production

Simple SummaryAlternative feed materials in poultry production are an important tool for sustainability and also improving animal performance, health status, and product quality. Thus, our present study aimed to investigate the usage possibility of algae as an alternative feed ingredient in poultry nutrition. In these regards, this study aimed to evaluate the nutritional value and production cost of three species of algae, namely Scenedesmus sp., Ankistrodesmus sp., and Synechococcaceae, harvested with batch and continuous cultivation processes. The current results clearly showed that the nutritional composition and amino acid profile of algae biomass harvested from three different microalgae species under batch and continuous cultivation practices are relatively higher and show variations in protein and lipid content. The current findings indicate the superiority of Scenedesmus sp. for its high PUFA and lysine content, and Synechocccaceae for its high content of methionine and threonine. Furthermore, Synechococcaceae could be offered as a natural additive for the pigmentation of egg yolk and broiler meat due to its darker shade of yellowness. It is important to emphasize that the nutritional value and production cost of microalgae must be considered to choose the right one as an alternative feedstuff.Recently, the demand for new alternative feedstuffs that do not contain chemical residue and are not genetically modified has been increased for sustainability in poultry production. In this respect, the usage of algae as animal feed is very promising as an alternative feed ingredient that reduces pollutant gases from animal production facilities. The aim of the current study is to investigate the usage possibility of algae, through determining nutritional value and production cost, as a feed ingredient in poultry nutrition. Three microalgae species, including Scenedesmus sp., Ankistrodesmus sp., and Synechococcaceae, were produced with batch and continuous cultivation to determine the difference in the lipid, protein, carbohydrate, fatty acid, and amino acid profiles, as well as the color characteristics and production cost. The highest lipid content of 72.5% was observed in algae biomass produced from Synechococcaceae with batch cultivation, whereas the highest protein level was found in algae biomass produced by Synechococcaceae under continuous cultivation practice (25.6%). The highest content of PUFA was observed in Scenedesmus sp. harvested from both batch and continuous cultivation (35.6 and 36.2%), whereas the lowest content of PUFA was found in Synechococcaceae harvested with continuous cultivation (0.4%). Continuously cultivated of Scenedesmus sp. had higher carbohydrate content than batch-cultivated Scenedesmus sp. (57.2% vs. 50.1%). The algae biomass produced from Synechococcaceae was found to have a higher content of essential amino acids, except lysine and histidine, compared to Scenedesmus sp. and Ankistrodesmus sp. Cultivation practices also affected the amino acid level in each algae species. The continuous cultivation practice resulted in a higher level of essential amino acids, except glycine. Synechococcaceae had richer essential amino acid content except for proline and ornithine, whereas continuous cultivation caused an incremental increase in non-essential amino acids. The lightness value was found to be the lowest (13.9) in Scenedesmus sp. that was continuously cultivated. The current study indicated that Scenedesmus sp. could be offered for its high PUFA and lysine content, whereas Synechococcaceae could have potential due to its high content of methionine and threonine, among the investigated microalgae and Cyanobacteria.

Using coffee waste as feedstock for continuous cultivation of Sulfolobus acidocaldarius.

Continuous microalgae cultivation in aquaculture wastewater by a membrane photobioreactor for biomass production and nutrients removal

Enhancing lipid production in microalgae Chlorella PY-ZU1 with phosphorus excess and nitrogen starvation under 15% CO2 in a continuous two-step cultivation process

Validation of a predictive model for fed-batch and continuous lipids production processes from acetic acid using the oleaginous yeast Cryptococcus curvatus

BACKGROUND: Poly‐β‐hydroxybutyrate (PHB) accumulation is triggered by limitation of a nutrient other than carbon. The production cost of PHB is very high. In order to reduce this cost, continuous cultivation for the accumulation of PHB was investigated. The culture was first allowed to grow under fed‐batch conditions to yield a significant increase in biomass and PHB accumulation. Thereafter this high‐cell‐density biomass containing PHB was allowed to grow and maintained under conditions of continuous cultivation so that the overall process could be simplified and economised.RESULTS: For continuous cultivation a medium containing 90 g L−1 fructose and 2.5 g L−1 nitrogen (as urea) was fed continuously at a dilution rate of 0.1 h−1. A steady state biomass of 27.7 g L−1 with a PHB concentration of 5.5 g L−1 was established in the bioreactor. This resulted in a continuous PHB productivity of 0.55 g L−1 h−1.CONCLUSION: The experiments have resulted in the development of a novel production technology involving the integration of batch, fed‐batch and continuous processes. At the same time the production of PHB under continuous cultivation increases the overall industrial importance of the system. Copyright © 2008 Society of Chemical Industry

Continuous production of selenomethionine-enriched Chlorella sorokiniana biomass in a photobioreactor

Development of cultivation strategies for friulimicin production in Actinoplanes friuliensis

Chapter 9 - Microbial lipids production by oleaginous yeasts

Lipid production by the red yeast Rhodosporidium toruloides was explored under nutrient limitation. To determine the compositional profiles of R. toruloides cells, samples were prepared using a continuous cultivation process under nutrient limitation and analyzed via several methods, including Fourier transform infrared spectroscopy and elemental analysis. Under nitrogen limitation, as the dilution rate increased, the cellular lipid content decreased but the carbohydrate and protein contents increased. Under carbon limitation, the cellular lipid, protein, and carbohydrate contents remained relatively constant at the different dilution rates. Moreover, the cellular elemental composition was essentially identical under nitrogen and carbon limitation at a high dilution rate of 0.20h-1. We also analyzed the consumed carbon to nitrogen (C/N) under different nutrition conditions. The results indicated that the consumed C/N had a major influence on cell metabolism and product formation, which contributed to our understanding of the physiological characteristics of R. toruloides.

Oleaginous yeasts are considered promising sources for lipid production due to their ability to accumulate high levels of lipids under appropriate growth conditions. The current study aimed to isolate and identify oleaginous yeasts having superior ability to accumulate high quantities of lipids; and enhancing lipid production using response surface methodology and repeated-batch fermentation. Results revealed that, twenty marine oleaginous yeasts were isolated, and the most potent lipid producer isolate was Candida parapsilosis Y19 according to qualitative screening test using Nile-red dye. Orange peels was used as substrate where C. parapsilosis Y19 produced 1.14 g/l lipids at 23.0% in batch fermentation. To enhance the lipid production, statistical optimization using Taguchi design through Response surface methodology was carried out. Total lipids were increased to 2.46 g/l and lipid content increased to 30.7% under optimal conditions of: orange peel 75 g/l, peptone 7 g/l, yeast extract 5 g/l, inoculum size 2% (v/v), pH 5 and incubation period 6 d. Furthermore, repeated-batch fermentation of C. parapsilosis Y19 enhanced lipid production where total lipids increased at 4.19 folds (4.78 g/l) compared to batch culture (before optimization). Also, the lipid content was increased at 1.7 folds (39.1%) compared to batch culture (before optimization). Fatty acid profile of the produced lipid using repeated-batch fermentation includes unsaturated fatty acids (USFAs) at 74.8% and saturated fatty acids (SFAs) at 25.1%. Additionally, in repeated-batch fermentation, the major fatty acid was oleic acid at 45.0%; followed by linoleic acid at 26.0%. In conclusion, C. parapsilosis Y19 is considered a promising strain for lipid production. Also, both statistical optimizations using RSM and repeated-batch fermentation are efficient methods for lipid production from C. parapsilosis Y19.

A continuous cultivation process for the fermentative production of succinic acid from glycerol with the recently isolated bacterium Basfia succiniciproducens DD1 was developed. Crude glycerol (5.1 g l(-1)) was used as C-source and NH(4)OH as N-source and pH-control agent. The problem of wall growth was solved by transfers of the cultivation broth into an empty identical fermentor. The resulting continuous cultivation process was maintained for more than 80 days. Glycerol-limited steady states were established for dilution rates between 0.004 and 0.018 h(-1). Higher dilution rates resulted in glycerol accumulation. Succinic acid concentrations, productivities, yields and specific productivities increased with increasing dilution rates: at 0.018 h(-1) the highest values were 5.21 g l(-1), 0.094 g l(-1) h(-1), 1.02 g g(-1) and 0.375 g g(-1) h(-1), respectively.

Predicting the fate of individual cells among a microbial population (i.e., growth and gene expression) remains a challenge, especially when this population is exposed to very dynamic environmental conditions, such as those encountered during continuous cultivation. Indeed, the dynamic nature of a continuous cultivation process implies the potential diversification of the microbial population resulting in genotypic and phenotypic heterogeneity. The present work focused on the induction of the arabinose operon in Escherichia coli as a model system to study this diversification process in continuous cultivations. As a preliminary step, the green fluorescent protein (GFP) level triggered by an arabinose-inducible ParaBAD promoter was tracked by flow cytometry in chemostat cultivations with glucose-arabinose co-feeding. For a wide range of glucose-arabinose co-feeding concentrations in the chemostats, the simultaneous occurrence of GFP positive and negative subpopulation was observed. In the second set of experiments, continuous cultivation was performed by adding glucose continuously and arabinose based on the capability of individual cells to switch from low GFP to high GFP expression states, performed with a technology setup called segregostat. In the segregostat cultivation mode, on-line flow cytometry analysis was used for adjusting the arabinose/glucose transitions based on the phenotypic switching profiles of the microbial population. This strategy allowed finding an appropriate arabinose pulsing frequency, leading to prolonged maintenance of the induction level with a limited increase in the phenotypic diversity for more than 60 generations. The results suggest that the steady forcing of individual cells into a given phenotypic trajectory may not be the best strategy for controlling cell populations. Instead, allowing individual cells to switch periodically around a predefined threshold seems to be a more robust strategy leading to oscillations, but within a predictable cell population behavior range.

Sustainable lipid production by oleaginous yeasts: Current outlook and challenges.

Concerns about climate change and the reliance on fossil fuel reserves have motivated researchers to identify new renewable sources of energy. Biomass holds the potential to replace fossil‐derived products with biofuels and bio‐based chemicals. Plant‐derived lipids are promising sources of biofuels; however, the production of plant oil often leads to the release of massive amounts of carbon dioxide due to deforestation and land‐use change. The production of biofuels via plant oils (such as soybean) also competes with food production and in turn, impacts biodiversity. To mitigate these issues, the production of lipids from oleaginous yeasts could be an excellent alternative by incorporating these microbes into biorefineries utilizing agricultural or forest residues. Eventually, these microbial lipids could be potential sources for producing lipid‐derived biofuels. However, the current conventional methods for the production and recovery of lipids from oleaginous microbes suffer from economic and ecological challenges that affect its industrial‐scale expansion. This review highlights the major economic and environmental bottlenecks for the production of lipid‐derived biofuels from oleaginous yeasts. It also provides perspectives on the strategies that could be adapted on economic and ecological fronts to assist the expansion of the production of microbial lipid‐derived biofuels at an industrial scale.