Maximum Dry Cell Weight Research Articles

Detoxification of a pyrolytic aqueous condensate from wheat straw for utilization as substrate in Aspergillus oryzae DSM 1863 cultivations

BackgroundThe pyrolytic aqueous condensate (PAC) formed during the fast pyrolysis of wheat straw contains a variety of organic carbons and might therefore potentially serve as an inexpensive substrate for microbial growth. One of its main components is acetic acid, which was recently shown to be a suitable carbon source for the filamentous fungus Aspergillus oryzae. However, the condensate also contains numerous toxic compounds that inhibit fungal growth and result in a tolerance of only about 1%. Therefore, to enable the use of the PAC as sole substrate for A. oryzae cultivations, a pretreatment seems to be necessary.ResultsVarious conditions for treatments with activated carbon, overliming, rotary evaporation and laccase were evaluated regarding fungal growth and the content of inhibitory model substances. Whereas the first three methods considerably increased the fungal tolerance to up to 1.625%, 12.5% and 30%, respectively, the enzymatic treatment did not result in any improvement. The optimum carbon load for the treatment with activated carbon was identified to be 10% (w/v) and overliming should ideally be performed at 100 °C and an initial pH of 12. The best detoxification results were achieved with rotary evaporation at 200 mbar as a complete removal of guaiacol and a strong reduction in the concentration of acetol, furfural, 2-cyclopenten-1-one and phenol by 84.9%, 95.4%, 97.7% and 86.2%, respectively, were observed. Subsequently, all possible combinations of the effective single methods were performed and rotary evaporation followed by overliming and activated carbon treatment proved to be most efficient as it enabled growth in 100% PAC shake-flask cultures and resulted in a maximum cell dry weight of 5.21 ± 0.46 g/L.ConclusionThis study provides a comprehensive insight into the detoxification efficiency of a variety of treatment methods at multiple conditions. It was revealed that with a suitable combination of these methods, PAC toxicity can be reduced to such an extent that growth on pure condensate is possible. This can be considered as a first important step towards a microbial valorization of the pyrolytic side-stream with A. oryzae.

Optimization of culture conditions of screened Galactomyces candidum for the production of single cell protein from biogas slurry

The use of single cell protein (SCP) has become a method for alleviating the shortage of protein feed that microorganisms propagate in a suitable culture medium. In this study, SCP was produced by yeast to use the nutrition contained in the biogas slurry of chicken manure. The results showed that Galactomyces candidum was the most efficient at producing SCP among the seven yeasts studied. The maximum cell dry weight (CDW) 6.79 g/L and protein content 39.39%, were obtained under the fermentation conditions of initial NH 4 + -N concentration of 2000 mg/L and a C/N ratio of 6:1 with acetate as the pH regulator. The total CDW increased to 9.24 g/L after secondary fermentation. Metal elements had a little effect on the growth of G. candidum . The addition of sulfur not only promoted the synthesis of sulfur-containing amino acid cysteine but also increased protein content by promoting the synthesis of glutamic acid and glutamine. Future experiments should focus more on achieving high-density cultivation and more efficient utilization of ammonia nitrogen in the biogas slurry. How to cite: Zhou P, Zhang L, Ding H, et al. Optimization of culture conditions of screened Galactomyces candidum for the production of single cell protein from biogas slurry. Electron J Biotechnol 2022;55. https://doi.org/10.1016/j.ejbt.2021.11.006

Swine wastewater treatment by combined process of iron carbon microelectrolysis-physical adsorption-microalgae cultivation.

Combined treatments were designed based on iron-carbon micro-electrolysis treatment (ICME), physical adsorption (PA) with zeolite (Z) or vermiculite (V) and microalgae cultivation (MC, Chlorella vulgaris) for removing pollutants from swine wastewater (SW): ICME + MC (IM), ICME + Z + MC (IZM) and ICME + V + MC (IVM). Results showed that the minimum total nitrogen (TN) of 43.66 mg L-1, NH4+-N of 1.33 mg-1 and total phosphorus (TP) of 0.14 mg-1 were obtained by IVM, while the minimum chemical oxygen demand (COD) was 105 mg-1 via IM. During the process of combined treatments, ICME contributed most to the removal of TN (84.52% by IZM), TP (97.78% by IVM and IZM) and COD (62.44% by IVM), and maximum NH4+-N removal (55.64%) was obtained by MC procedure in IM process. Vermiculite performed better than zeolite during all the combined treatments. Besides, the maximum cell dry weight (CDW, 0.74 g-1) of C. vulgaris was obtained by IM on day 13. The results provide an efficient integrated method for swine wastewater treatment.

An innovative strategy of recycling miscellaneous waste carbohydrates from high-fructose syrup production for Pichia pastoris fermentation

Recycling waste carbon source for fermentation is of great interests and high practical value. However, the process suffered some problems like unclear carbohydrate composition, low nutrition content, presence of various contaminants and high cost for pretreatment. Currently, the high-fructose syrup (HFS) production industry in China generates a large amount of waste liquid containing miscellaneous waste carbohydrates (MWC), which has a notable environmental impact. To recycle MWC for Pichia pastoris fermentation, the composition of MWC was analyzed and the fermentation processes were optimized. The composition of MWC was determined as 802.3 g L−1 total carbohydrate, 480 g L−1 glucose, 92 g L−1 fructose, 103.6 g L−1 maltose, 36.8 g L−1 maltotriose and 89.9 g L−1 other oligosaccharides with different degrees of polymerization (DPs 4–16). After the fermentation medium and conditions for pGAP/pAOX1-P. pastoris were optimized, MWC were employed as the alternative carbon source to culture the two strains to produce endo-β-1,3-glucanase in 7-L bioreactors. Using MWC for pGAP-P. pastoris culture, the dry cell weight (DCW) and endo-β-1,3-glucanase activity reached 69.1 g L−1 and 171.8 U mL−1, respectively, which were the same levels as in the batch using glucose as the carbon source. When using MWC and the self-designed DO-Stat-Time feeding strategy for pAOX1-P. pastoris culture, the maximum DCW and enzyme activity reached 83.6 g L−1 and 212.3 U mL−1, which improved 41.4% and 34.9%, respectively compared with the control group. This study established cleaner production procedures for both HFS and P. pastoris fermentation industries by considerably reducing environmental pollution and decreasing the production cost.

Efficient Production of Polyhydroxyalkanoate Through Halophilic Bacteria Utilizing Algal Biodiesel Waste Residue.

The objective of the current work was to investigate the potential of halophilic bacterial isolates for efficient utilization of crude glycerol from algal biodiesel waste into polyhydroxyalkanoates (PHAs) a green plastic. Screening of the isolates was directly done in algal biodiesel waste residue containing solid agar plates supplemented with Nile red. Crude glycerol is a biodiesel waste whose bioconversion into value-added products provides an alternative for efficient management with dual benefit. For the scale-up studies of PHAs, Halomonas spp. especially H. daqingensis was observed as a potential candidate growing well in 3% Algal biodiesel waste residue (ABWR), 5% NaCl supplementation at 35°C within 48 h of incubation. Maximum Cell dry weight (CDW) of 0.362 ± 0.001 g and 0.236 ± 0.003 g PHA was obtained with H. daqingensis when grown in the fermentor with 0.5 vvm air flow rate and 200 rpm containing 3% ABWR supplemented with 5% NaCl at 35°C incubation temperature for 48 h. ABWR can serve as a sole substrate for PHA production at an industrial scale serving two approaches: getting rid of the biodiesel industrial waste containing high amount of glycerol besides using waste replacing commercial substrate thereby reducing the cost of the product.

The selective breeding and mutagenesis mechanism of high‐yielding surfactin Bacillus subtilis strains with atmospheric and room temperature plasma

Surfactin, a good biological surfactant, is derived from the metabolites of microorganisms. However, the ability of natural strains to produce surfactin is low, and so the presented study aimed to use a novel mutagenesis technology to increase their yields. Atmospheric and room temperature plasma (ARTP) was used to conduct mutation breeding of Bacillus subtilis CICC 10721, and a mutant strain M45 with a higher surfactin yield of 34.2% and a stable subculture was screened out. From the fermentation kinetics study, it was found that the maximum cell dry weight, maximum growth rate and surfactin synthesis parameters of the mutant strain M45 were all greater than that of the original strain. Scanning electron microscope and laser scanning confocal microscope observations showed that the spore morphology changed after ARTP treating, and the intracellular Ca2+ concentration of the mutant increased. Genome resequencing analysis showed that 66 single nucleotide poymorphism non-synonymous mutation sites occurred in M45, and the identification results of the fermentation broth extract from M45 showed that it is composed of C12 -C16 surfactin. ARTP mutagenesis was found to change the morphology of bacteria, membrane permeability and genes related to the synthesis and secretion of surfactin. The present study provides a basis for industrial production of surfactin and an understanding of the mutagenesis mechanism. © 2021 Society of Chemical Industry.

Unveiling the induced lipid production in Chlorella vulgaris under pulsed magnetic field treatment

The pulsed magnetic field (PMF) was adopted for the enhancement of lipid in Chlorella vulgaris. The average biomass and lipid content in outdoor conditions were found to be 0.315 g.L−1 and 20–25% respectively. The effect of magnetic flux density in the range of 600–900 mG on biomass production and lipid content was studied. A magnetic flux density of 700 mG at 1Hz for 4 h per day was found to be optimum, which yielded a maximum dry cell weight of 0.61 g.L−1, two-fold than the normal condition, with a lipid content of 55.2%. FTIR analysis evidenced that the PMF treatment increased the active oxygen, which could be attributed to the enhancement of growth and lipid of C. vulgaris.

Screening of the strictly xylose-utilizing Bacillus sp. SM01 for polyhydroxybutyrate and its co-culture with Cupriavidus necator NCIMB 11599 for enhanced production of PHB

Polyhydroxybutyrate (PHB) is a biodegradable plastic that can be used as an alternative to petrochemical-based plastics. PHB is produced by various microorganisms such as Ralstonia, Halomonas, and Bacillus species. However, there are very few strains that produce PHB using xylose, an abundant and inexpensive carbon source. In this study, ten xylose-utilizing PHB producers isolated from South Korean marine environments were screened and characterized. Among these isolates, Bacillus sp. SM01, a newly identified strain, produced the highest amount of PHB using xylose. Under optimal conditions, the maximum dry cell weight (DCW) was 3.41 ± 0.09 g/L, with 62% PHB content, and Bacillus sp. SM01 showed Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer production with propionate; however, the growth of Bacillus sp. SM01 was greatly inhibited by the presence of glucose. Co-culturing Bacillus sp. SM01 with Cupriavidus necator NCIMB 11599 resulted in increased DCW, PHB production, and utilization of glucose and xylose, the main sugar of lignocellulosic biomass, compared with the monoculture. Our results indicated that this co-culture system can be used to increase PHB production and overcome the limitation of sugar consumption associated with Bacillus sp. SM01 and C. necator.

Pemanfaatan Hidrolisat Talas (Colocasia esculenta L.) pada Kultur Miksotrofik Mikroalga Tetraselmis chui: Pengamatan Pertumbuhan dan Kadar Lipida

This study aims to observe the potential use of taro hydrolysate (Colocasia esculenta L.) as a source of complex organic carbon to produce optimum cell density, biomass, lipid and chlorophyll content from T. chui microalgae under myxotrophic conditions. The culture was carried out in a vial containing 400 mL of bold basal medium. Taro hydrolysate is given in five concentrations, namely: 0, 5, 10, 15 and 20 g/L. The results showed that T. chui microalgae could grow in myxotrophic conditions with the addition of taro hydrolysate in the concentration range of 5 to 20 g/L. The maximum cell density and dry weight in the addition of 10 g/L taro hydrolysate were 4.23 x 105 cells/ml and 0.57 g/L, respectively. Meanwhile, the maximum fresh weight and lipid content were achieved at the addition of 15 g/L taro hydrolysate, namely 4.85 g/L and 67.4%. Chlorophyll content decreased with increasing concentration of taro hydrolysate. In conclusion, the use of taro hydrolysate can increase cell density, fresh weight and dry weight, lipid content and decrease the chlorophyll content of T.chui microalgae in myxotrophic culture.
 Keywords: Taro Hydrolysate, Lipid, Mixotrophic, Growth, Tetraselmis chui

Effect of Eurotium cristatum fermentation on the α-glucosidase inhibitory activity of mulberry leaves alkaloids

Eurotium cristatum CY-1 was used for the solid-stated fermentation of mulberry leaves (ML) with the purpose of enhancing the alkaloids content and α-glucosidase inhibitory activity of ML through microbial fermentation. The results indicated that Eurotium cristatum CY-1 grown well when cultivated with MLs as substrate. The maximum cell dry weight of 393.32 mg was reached on the 10 d of fermentation. The alkaloids content of ML was increased with the fermentation time, and the maximum value of 8.711 mg/g was obtained at 8 d of fermentation, which was increased by171.96% compared to that extracted from unfermented ML. The α-glucosidase inhibitory efficiency was also improved along with the fermentation time. The IC50 values of alkaloid extracted from 8d-fermented mulberry leaves was 3.94 μg/mL, but 6.82 μg/mL of the alkaloid extracted from the unfermented ML. Therefore, the fermentation of Eurotium cristatum could benefit for enhancing the alkaloid content and α-glucosidase inhibitory efficiency of ML. It would provide a valuable strategy for obtain safe and low-cost α-glucosidase inhibitors from natural herbal medicines.

Enhance the flavonoids content and α-glucosidase inhibitor efficiency of mulberry leaves by fermented with Ganoderma lucidum

Diabetes is a kind of chronic disease that seriously threatens human health. α-glucosidase inhibitors are an effective way to inhibit the increase of postprandial blood glucose. Mulberry leaf flavonoids can be used as highly effective α-glucosidase inhibitors, but usually in low concentrations. Microbial fermentation is an effective method to increase the content of flavonoids in plants. In this paper, the fermentation of mulberry leaves with Ganoderma lucidum was conducted to investigate the cell growth of microbial, the content and α-glucosidase inhibitory efficiency of flavonoids in mulberry leaves. The results indicated that mulberry leaves can satisfy the nutritional needs of G. lucidum, and the maximum cell dry weight of 393.32 mg was obtained after a 10 d of fermentation. The flavonoid content in mulberry leaves was increased significantly with the fermentation time. Compared to unfermented mulberry leaves, the flavonoid content in mulberry leaves fermented for 8 d increased by 56.5%. The inhibitory efficiency of the fermented flavonoids was also significantly improved. The IC50 of α-glucosidase of flavonoids extracted from 8 d fermented mulberry leaves and unfermented mulberry leaves were 0.041 mg/mL and 0.01 mg/mL, respectively. This article will provide a reference for the enrichment of functional active ingredients in plants through microbial fermentation technology.

Evaluating the Engineered Saccharomyces cerevisiae With High Spermidine Contents for Increased Tolerance to Lactic, Succinic, and Malic Acids and Increased Xylose Fermentation

Saccharomyces cerevisiae is a promising candidate for production of organic acids as it is more tolerant to these acids than the prokaryotes. However, the large-scale production of organic acids from lignocellulosic biomass is limited by their accumulation in the growth medium and inability of xylose fermentation by S. cerevisiae. Here we showed that high intracellular spermidine (SPD) contents confers enhanced tolerance to lactic, succinic, and malic acids in S. cerevisiae. Specifically, in the presence of 20 g/L malic acid, the maximum specific growth rate and dry cell weight of a S. cerevisiae with two fold higher SPD content were 40% and 36% higher than those of the control strain. When a xylose assimilation pathway was introduced into an engineered strain with high SPD content, the resulting S. cerevisiae strain exhibited 23∼47% higher xylose consumption rate and 6∼16% higher ethanol productivity than those of the control strain during the four times of repeated-batch fermentations using a mixture of glucose and xylose as carbon sources. These results suggest that the strain developed in this study would serve as a platform strain for production of organic acids.

Establishment of callus and cell suspension culture of Sophora alopecuroides Linn. for the production of oxymatrine

Oxymatrine is one of the most important biologically active compounds and is present in Sophora alopecuroides L. The present investigation focuses on the development of an efficient tissue culture method to induce callus and cell suspension culture of S. alopecuroides by studying the effect of jasmonic acid and nitric oxide on cell suspension culture. Callus induction efficiency is high in axenic leaf explants grown in MS medium supplemented with 1.0 mg/L Kinetin (Kin), 1.0 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D). The cell suspension culture was developed using the same callus induction medium without agar. The maximum cell number and dry weight of suspension culture were obtained by the 9th day of incubation. The synthesis of oxymatrine is higher in jasmonic acid and nitric oxide (200 µMJA and 50 µMNO) combination (11.91 µg/g) when compared to the non-elicited control (8.3 µg/g) of callus.

Lipid Production by Yeasts Growing on Commercial Xylose in Submerged Cultures with Process Water Being Partially Replaced by Olive Mill Wastewaters

Six yeast strains belonging to Rhodosporidium toruloides, Lipomyces starkeyi, Rhodotorula glutinis and Cryptococcus curvatus were shake-flask cultured on xylose (initial sugar—S0 = 70 ± 10 g/L) under nitrogen-limited conditions. C. curvatus ATCC 20509 and L. starkeyi DSM 70296 were further cultured in media where process waters were partially replaced by the phenol-containing olive mill wastewaters (OMWs). In flasks with S0 ≈ 100 g/L and OMWs added yielding to initial phenolic compounds concentration (PCC0) between 0.0 g/L (blank experiment) and 2.0 g/L, C. curvatus presented maximum total dry cell weight—TDCWmax ≈ 27 g/L, in all cases. The more the PCC0 increased, the fewer lipids were produced. In OMW-enriched media with PCC0 ≈ 1.2 g/L, TDCW = 20.9 g/L containing ≈ 40% w/w of lipids was recorded. In L. starkeyi cultures, when PCC0 ≈ 2.0 g/L, TDCW ≈ 25 g/L was synthesized, whereas lipids in TDCW = 24–28% w/w, similar to the experiments without OMWs, were recorded. Non-negligible dephenolization and species-dependent decolorization of the wastewater occurred. A batch-bioreactor trial by C. curvatus only with xylose (S0 ≈ 110 g/L) was performed and TDCW = 35.1 g/L (lipids in TDCW = 44.3% w/w) was produced. Yeast total lipids were composed of oleic and palmitic and to lesser extent linoleic and stearic acids. C. curvatus lipids were mainly composed of nonpolar fractions (i.e., triacylglycerols).

Replacement of Sodium Bicarbonate and Micronutrients in Kosaric Medium With Banana Leaf Ash Extract for Culture of Spirulina Platensis

Spirulina platensis is one of the most promising microalgae for culture due to its high nutritional values. The main constraint to its production is the high cost of culture media. Therefore, an experiment was conducted to evaluate the growth performance of S. platensis with the aim of replacing sodium bicarbonate (NaHCO3) and mineral nutrients in Kosaric medium (KM) with banana leaf ash extract. KM was used as control medium in treatment T1. In treatments T2 to T5, 50% of NaHCO3 in KM was replaced with banana leaf ash extract (BLAE). In addition, micronutrients in KM were reduced to 75%, 50% and 25% in treatments T3 to T5, respectively. The values of different physical and chemical parameters (temperature, pH, dissolved oxygen and light intensity) of the culture media were within the suitable range for S. platensis culture. Optical density in treatments T2 and T3 were similar to that was in treatment T1. Maximum cell dry weight (0.65 gL-1) was observed in treatment T1 and it was similar to the treatments T2 and T3 where 50% of NaHCO3 in KM was replaced with banana leaf ash extract with 100% and 75% micronutrients supply, respectively. The similar trend was found in chlorophyll a content. It was evident that 50% of NaHCO3 in KM can be replaced with BLAE for the culture of S. platensis, in addition micronutrients in KM can be reduced to 75%.
 Ann. Bangladesh Agric. (2019) 23(1) : 37-47

Microbioreactor for lower cost and faster optimisation of protein production.

Optimisation of bioprocesses relies on approaches that are either labour intensive or require expensive robotic systems. There is a need for fluidic processing at low volume that can be integrated with existing bioprocess analytics to provide analytical information for the development and optimisation of bioprocesses. We demonstrate a 1 mL polymer inkjet 3D printed (i3DP) microbioreactor with integrated sensing (pH, oxygen and cell density) for optimisation of recombinant protein production with different feeds. A pressurised fluid driving system was used to control flow rates down to 0.7 μL min-1 with fluid switching from four reservoirs using a manifold controlled by solenoid valves. Oxygen transferred from a headspace via a gas-permeable membrane achieved a kLa of up to 90 h-1 at 1500 rpm. Cultivation of E. coli within the microbioreactor was comparable with a 2 L bench scale bioreactor, with optical densities of respectively 7.1 ± 0.4 and 6.5 ± 0.35. Triplicate batch cultivations within the microbioreactor of Pichia pastoris, with diauxic growth on glycerol (0.20 ± 0.02 h-1) and methanol (0.02 ± 0.04 h-1), showed good control of pH and DO and achieved a maximum dry cell weight of 10 ± 1 g L-1. For continuous cultivations, recombinant protein production was higher in pure methanol (314 ± 23) than methanol-sorbitol (202 ± 17) but reduces over time with lower cellular viability for methanol-glucose mixed feed, with less total protein produced and increases in DNA and proteases released. The developed system could be used in different applications including within synthetic biology, cell and gene therapy and organ-on-chips.

Assessing the robust growth and lipid-accumulating characteristics of Scenedesmus sp. for biodiesel production.

In the present investigation, different salts of nitrogen and carbon sources were tested for their potential to boost biomass and lipid content in Scenedesmus sp. IITRIND2. Among the nitrogen sources, ammonium bicarbonate/nitrate cultures showed maximum dry cell weight (DCW) of ~ 1.8g/L and lipid yield (~ 40%) while the addition of C6 sugars (glucose and mannose) and sodium acetate enhanced the DCW (~ 3g/L) and lipid accumulation (~ 40%) compared with disaccharides, C4 and C5 sugars. On evaluating the synergistic effects of the nitrogen and carbon sources, maximum DCW (3.66g/L) was obtained in ammonium bicarbonate + sodium acetate cultures with a lipid yield of 37.15%. The fatty acid profile of the derived biodiesel was similar to that of plant oils. The results clearly established the robust capability of the novel microalga to efficiently adapt, sustain, and grow in different carbon and nitrogen sources along with high lipid productivity, making it a potential source for biodiesel production.

Effects of gluconate on biomass improvement and light stress tolerance of Haematococcus pluvialis in mixotrophic culture

Mixotrophic culture shows great potential for improving microalgal growth. Currently, the complex roles of organic carbon for biomass enhancement in mixotrophic culture remain a topic of investigation. In this study, the green microalgae Haematococcus pluvialis was cultured for biomass production under mixotrophic conditions using a new organic carbon source, sodium gluconate. Experiments feeding H. pluvialis with sodium gluconate, sodium acetate, and ribose were conducted. The best growth performance was achieved with sodium gluconate exposed to high light intensity. With the addition of 2 g/L gluconate, the maximum cell number achieved 2.43 × 106/mL at 105 ± 3 μmol m−2 s−1 light intensity, a five-fold increase over that of heterotrophic culture and 89.8% increase over ribose-fed mixotrophic culture. The maximum dry cell weight was 2.09 g/L with a specific growth rate of 0.48 d−1, an increase of 77.1% over that with optimal ribose conditions. The cellular motility of microalgae was affected by the culture age and light intensity. At lower light intensity (45 ± 3 μmol m−2 s−1), the highest motile cell number was 7.33 × 105/mL with gluconate. Under mixotrophic conditions, the culture with gluconate kept high numbers of motile cells with the increase of light intensity, 3.17 × 105/mL at 105 ± 3 μmol m−2 s−1. Even high light intensity caused decrease in cellular motility, gluconate-fed microalgae still had active cell activity with more motile cells compared with that fed with ribose. Microalgae with gluconate triggered resistant response against high light intensity under mixotrophic conditions. Moreover, H. pluvialis showed great potential in effective photosynthesis with higher chlorophyll content under high light condition. These results indicate that gluconate is an effective organic carbon source for improving biomass productivity, cell activity, and photosynthesis efficiency for H. pluvialis in mixotrophic culture.

Consumption of sugars and inhibitors of softwood hemicellulose hydrolysates as carbon sources for polyhydroxybutyrate (PHB) production with Paraburkholderia sacchari IPT 101

The future industrial success of the compostable bio-polyesters known as polyhydroxyalkanoates, which includes polyhydroxybutyrate (PHB), depends mainly on their production using cheaper carbon sources than food-derived glucose. The existing pulp and paper infrastructure enables an alternative sugar supply in the form of wood hydrolysates. Softwood hemicellulose hydrolysates have a favourable sugar profile for fermentations and can be produced in such emerging integrated forest biorefineries. The processes can lead to varying amounts of inhibitors which can lead to the reduction or prevention of bacterial growth. A dilute acid pretreatment was used to produce a softwood hemicellulose hydrolysate containing the sugars mannose, xylose, glucose, galactose, and arabinose. To study the effects of increasing sugar diversity and inhibitor concentration, the softwood hydrolysate was mixed in varying proportions with a hardwood holocellulose hydrolysate obtained from the TMP-Bio process (a thermomechanical pulping-based process producing glucose and xylose). In fermentations with Paraburkholderia sacchari IPT 101, the sugars were depleted at different rates in the following order: glucose, mannose, xylose, galactose, and arabinose. All potential inhibitors except phenols were metabolized. The maximum cell dry weight reached 6.7 ± 0.1 g/L with 71 ± 5% PHB with hardwood holocellulose hydrolysate after 48 h. The analyses of the sugar and inhibitor consumption provided valuable information to validate approaches for the detoxification of softwood hemicellulose hydrolysates. Overall, the detoxification would allow PHB production in an integrated softwood biorefinery scheme.

Utilization of Clarified Butter Sediment Waste as a Feedstock for Cost-Effective Production of Biodiesel.

The rising demand and cost of fossil fuels (diesel and gasoline), together with the need for sustainable, alternative, and renewable energy sources have increased the interest for biomass-based fuels such as biodiesel. Among renewable sources of biofuels, biodiesel is particularly attractive as it can be used in conventional diesel engines without any modification. Oleaginous yeasts are excellent oil producers that can grow easily on various types of hydrophilic and hydrophobic waste streams that are used as feedstock for single cell oils and subsequently biodiesel production. In this study, cultivation of Rhodosporidium kratochvilovae on a hydrophobic waste (clarified butter sediment waste medium (CBM)) resulted in considerably high lipid accumulation (70.74% w/w). Maximum cell dry weight and total lipid production were 15.52 g/L and 10.98 g/L, respectively, following cultivation in CBM for 144 h. Neutral lipids were found to accumulate in the lipid bodies of cells, as visualized by BODIPY staining and fluorescence microscopy. Cells grown in CBM showed large and dispersed lipid droplets in the intracellular compartment. The fatty acid profile of biodiesel obtained after transesterification was analyzed by gas chromatography-mass spectrometry (GC–MS), while its quality was determined to comply with ASTM 6751 and EN 14214 international standards. Hence, clarified sediment waste can be exploited as a cost-effective renewable feedstock for biodiesel production.