Efficient Using Durian Shell Hydrolysate as Low-Cost Substrate for Bacterial Cellulose Production by <Emphasis Type="Italic">Gluconacetobacter xylinus</Emphasis>

Durian is one important tropical fruit with high nutritional value, but its shell is usually useless and considered as waste. To explore the efficient and high-value utilization of this agricultural and food waste, in this study, durian shell was simply hydrolyzed by dilute sulfuric acid, and the durian shell hydrolysate after detoxification was used for bacterial cellulose (BC) production by Gluconacetobacter xylinus for the first time. BC was synthesized in static culture for 10 days and the highest BC yield (2.67 g/L) was obtained at the 8th day. The typical carbon sources in the substrate including glucose, xylose, formic acid, acetic acid, etc. can be utilized by G. xylinus. The highest chemical oxygen demand (COD) removal (16.40%) was obtained at the 8th day. The highest BC yield on COD consumption and the highest BC yield on sugar consumption were 93.51% and 22.98% (w/w), respectively, suggesting this is one efficient bioconversion for BC production. Durian shell hydrolysate showed small influence on the BC structure by comparison with the structure of BC generated in traditional Hestrin–Schramm medium detected by FE-SEM, FTIR, and XRD. Overall, this technology can both solve the issue of waste durian shell and produce valuable bio-polymer (BC).     

Use of elephant grass (Pennisetum purpureum) acid hydrolysate for microbial oil production by Trichosporon cutaneum

Elephant grass (Pennisetum purpureum) dilute acid hydrolysate contains 34.6?g/L total sugars. The potential of lipid production by oleaginous yeast Trichosporon cutaneum grown on elephant grass acid hydrolysate was investigated for the first time. During the fermentation process on the elephant grass acid hydrolysate, glucose, xylose, and arabinose could be well utilized as carbon sources by T. cutaneum. Interestingly, xylose was almost no use before glucose was consumed completely. This illustrated that simultaneous saccharification of xylose and glucose by T. cutaneum did not occur on elephant grass acid hydrolysate. The highest biomass, lipid content, lipid yield, and lipid coefficient of T. cutaneum were measured after the sixth day of fermentation and were 22.76?g/L, 24.0%, 5.46?g/L, and 16.1%, respectively. Therefore, elephant grass is a promising raw material for microbial oil production by T. cutaneum.     

CRISPR/dCas9干扰bcsD基因表达调控细菌纤维素结构

木葡糖酸醋杆菌(Gluconacetobacter xylinus)是细菌纤维素的主要生产菌株。在该菌中,BcsD是纤维素合酶的亚基之一,参与细菌纤维素的组装过程。利用CRISPR/dCas9系统调控bcsD基因的表达量,获得了一系列bcsD基因表达量不同的木葡糖酸醋杆菌。通过分析细菌纤维素的结构特征发现,细菌纤维素的结晶度和孔隙率随着木葡糖酸醋杆菌中bcsD表达量的变化而发生改变。其中孔隙率的变化范围在59.95%–84.05%之间,结晶度的变化范围在74.26%–93.75%之间,而细菌纤维素的产量并未因bcsD的表达量变化而发生显著下降。结果表明,bcsD的表达量低于55.34%后,细菌纤维素的孔隙率显著上升,并且细菌纤维素的结晶度与bcsD的表达量呈正相关。最终,通过干扰bcsD基因的表达,实现了一步发酵木葡糖酸醋杆菌获得了产量稳定且结构不同的细菌纤维素。     

Lumping kinetics of ABE fermentation wastewater treatment by oleaginous yeast Trichosporon cutaneum

Lumping kinetics models were built for the biological treatment of acetone–butanol–ethanol (ABE) fermentation wastewater by oleaginous yeast Trichosporon cutaneum with different fermentation temperatures. Compared with high temperature (33°C, 306?K) and low temperature (23°C, 296?K), medium temperature (28°C, 301?K) was beneficial for the cell growth and chemical oxygen demand (COD) degradation during the early stage of fermentation but the final yeast biomass and COD removal were influenced little. By lumping method, the materials in the bioconversion network were divided into five lumps (COD, lipid, polysaccharide, other intracellular products, other extracellular products), and the nine rate constants (k₁–k₉) for the models can well explain the bioconversion laws. The Gibbs free energy (G) for this bioconversion was positive, showing that it cannot happen spontaneous, but the existence of yeast can after the chemical equilibrium and make the bioconversion to be possible. Overall, the possibility of using lumping kinetics for elucidating the laws of materials conversion in the biological treatment of ABE fermentation wastewater by T. cutaneum has been initially proved and this method has great potential for further application.     

Candida zeylanoides as a new yeast model for lipid metabolism studies: effect of nitrogen sources on fatty acid accumulation

Lipid homeostasis is well-known in oleaginous yeasts, but there are few non-oleaginous yeast models apart from Saccharomyces cerevisiae. We are proposing the non-oleaginous yeast Candida zeylanoides QU 33 as model. The aim of this study was to investigate the influence of the carbon/nitrogen ratio and the type of nitrogen source upon oil accumulation by this yeast grown on shake flask cultures. The maximum biomass was obtained in yeast extract (2.39?±?0.19 g/l), followed by peptone (2.24?±?0.05 g/l), while the highest content of microbial oil (0.35?±?0.01 g/l) and the maximum lipid yield (15.63 %) were achieved with peptone. Oleic acid was the predominant cellular fatty acid in all culture media (>32.23 %), followed by linoleic (>15.79 %) and palmitic acids (>13.47 %). The highest lipid yield using glucose and peptone was obtained at the C/N ratio of 200:1.     

Beneficial Effect of Corncob Acid Hydrolysate on the Lipid Production by Oleaginous Yeast Trichosporon dermatis

In this work, corncob acid hydrolysate and its simulated medium whose sugar composition was the same as the corncob acid hydrolysate were used as fermentation substrate for lipid production by oleaginous yeast Trichosporon dermatis. On the corncob acid hydrolysate, after 7 days of fermentation, the biomass, lipid content, lipid yield, and lipid coefficient of T. dermatis were 17.3 g/L, 40.2%, 7.0 g/L, and 16.5%, respectively. Interestingly, during the lipid fermentation on the corncob acid hydrolysate, glucose, xylose, arabinose, and even acetic acid could be well utilized as carbon sources by T. dermatis. Surprisingly, the lipid yield (7.0 g/L) of T. dermatis on the corncob acid hydrolysate was much higher than that (3.8 g/L) on the simulated medium, in spite of the fact that the lipid coefficient (17.4%) on the simulated medium was a little higher. This phenomenon further showed that lignocellulosic acid hydrolysate was a suitable substrate for lipid fermentation by T. dermatis. This work would help the comprehensive utilization of lignocellulosic biomass for lipid production.     

Beneficial Effect of Acetic Acid on the Xylose Utilization and Bacterial Cellulose Production by Gluconacetobacter xylinus

In this work, acetic acid was found as one promising substrate to improve xylose utilization by Gluconacetobacter xylinus CH001. Also, with the help of adding acetic acid into medium, the bacterial cellulose (BC) production by G. xylinus was increased significantly. In the medium containing 3 g l⁻¹ acetic acid, the optimal xylose concentration for BC production was 20 g l⁻¹. In the medium containing 20 g l⁻¹ xylose, the xylose utilization and BC production by G. xylinus were stimulated by acetic acid within certain concentration. The highest BC yield (1.35 ± 0.06 g l⁻¹) was obtained in the medium containing 20 g l⁻¹ xylose and 3 g l⁻¹ acetic acid after 14 days. This value was 6.17-fold higher than the yield (0.21 ± 0.01 g l⁻¹) in the medium only containing 20 g l⁻¹ xylose. The results analyzed by FE-SEM, FTIR, and XRD showed that acetic acid affected little on the microscopic morphology and physicochemical characteristics of BC. Base on the phenomenon observed, lignocellulosic acid hydrolysates (xylose and acetic acid are main carbon sources present in it) could be considered as one potential substrate for BC production.     

Bioprospecting microbes for single-cell oil production from starchy wastes

Production of lipid from oleaginous yeast using starch as a carbon source is not a common practice; therefore, the purpose of this investigation was to explore the capability of starch assimilating microbes to produce oil, which was determined in terms of biomass weight, productivity, and lipid yield. Saccharomyces pastorianus, Rhodotorula mucilaginosa, Rhodotorula glutinis, and fungal isolate Ganoderma wiiroense were screened for the key parameters. The optimization was also performed by one-factor-at-a-time approach. Considering the specific yield of lipid and cell dry weight yield, R. glutinis and R. mucilaginosa showed superiority over other strains. G. wiiroense, a new isolate, would also be a promising strain for starch waste utilization in terms of extracellular and intracellular specific yield of lipids. Extracellular specific yield of lipid was highest in R. glutinis culture (0.025?g?g^?1 of biomass) followed by R. mucilaginosa (0.022?g?g^?1 of biomass) and G. wiiroense (0.020?g?g^?1 of biomass). Intracellular lipid was again highest in R. glutinis (0.048?g?g^?1 of biomass). The most prominent fatty acid methyl esters among the lipid as detected by GC-MS were saturated lipids mainly octadecanoic acid, tetradecanoate, and hexadecanoate. Extracellular lipid produced on starch substrate waste would be a cost-effective alternative for energy-intensive extraction process in biodiesel industry.     

Metabolic flux analysis of Gluconacetobacter xylinus for bacterial cellulose production

Metabolic flux analysis was used to reveal the metabolic distributions in Gluconacetobacter xylinus (CGMCC no. 2955) cultured on different carbon sources. Compared with other sources, glucose, fructose, and glycerol could achieve much higher bacterial cellulose (BC) yields from G. xylinus (CGMCC no. 2955). The glycerol led to the highest BC production with a metabolic yield of 14.7 g/mol C, which was approximately 1.69-fold and 2.38-fold greater than that produced using fructose and glucose medium, respectively. The highest BC productivity from G. xylinus CGMCC 2955 was 5.97 g BC/L (dry weight) when using glycerol as the sole carbon source. Metabolic flux analysis for the central carbon metabolism revealed that about 47.96 % of glycerol was transformed into BC, while only 19.05 % of glucose and 24.78 % of fructose were transformed into BC. Instead, when glucose was used as the sole carbon source, 40.03 % of glucose was turned into the by-product gluconic acid. Compared with BC from glucose and fructose, BC from the glycerol medium showed the highest tensile strength at 83.5 MPa, with thinner fibers and lower porosity. As a main byproduct of biodiesel production, glycerol holds great potential to produce BC with superior mechanical and microstructural characteristics.     

Direct bioconversion of rice residue from canteen waste into lipids by new amylolytic oleaginous yeast Sporidiobolus pararoseus KX709872

The new amylolytic oleaginous red yeast, Sporidiobolus pararoseus KX709872, produced both α-amylase (540?±?0.09?mU/mL) and amyloglucosidase (23?±?0.00?mU/mL) and showed good ability to directly convert rice residue from canteen waste to biomass and lipids. Effects of medium composition and cultivation conditions on growth and lipid accumulation for strain KX709872 were investigated under shaking flask and upscaling levels. At C?:?N ratio of 25?:?1, pH 5.45, 22.36°C, and 199.40?rpm for 7 days, volumetric production of biomass and lipids, lipid content, and lipid productivity reached 17.69?±?0.44, 8.35?±?0.19?g/L, 49.48?±?0.41% (w/w), and 1.67?±?0.11?g/L/day, respectively. Production of lipids was also implemented in 5.0-L stirred tank bioreactor with 2.5?L of optimized medium at 300?rpm and 3.0 vvm for 5 days. Volumetric production of biomass and lipids, lipid content, and lipid productivity were 16.33?±?0.49, 8.75?±?0.13?g/L, 56.61?±?0.04% (w/w), and 2.19?±?0.03?g/L/day, respectively. Meanwhile, the fatty acids of lipids from strain KX709872 had high oleic acid content (60?62%) which was similar to those of vegetable oils, indicating that these lipids are promising as an alternative biodiesel feedstock. Moreover, the biodiesel derived from lipids of strain KX709872 had properties satisfying the criteria of ASTM D6751 and EN 14214 standards.     

Process optimization for the production of diosgenin with Trichoderma reesei

Based on the response surface methodology, an effective microbial system for diosgenin production from enzymatic pretreated Dioscorea zingiberensis tubers with Trichoderma reesei was studied. The fermentation medium was optimized with central composite design (3⁵) depended on Plackett–Burmann design which identified significant impacts of peptone, K₂HPO₄ and Tween 80 on diosgenin yield. The effects of different fermentation conditions on diosgenin production were also studied. Four parameters, i.e. incubation period, temperature, initial pH and substrate concentration were optimized using 4⁵ central composite design. The highest diosgenin yield of 90.57% was achieved with 2.67% (w/v) of peptone, 0.29% (w/v) of K₂HPO₄, 0.73% (w/v) of Tween 80 and 9.77% (w/v) of substrate, under the condition of pH 5.8, temperature 30 °C. The idealized incubation time was 6.5 days. After optimization, the product yield increased by 33.70% as compared to 67.74 ± 1.54% of diosgenin yield in not optimized condition. Scale-up fermentation was carried out in a 5.0 l bioreactor, maximum diosgenin yield of 90.17 ± 3.12% was obtained at an aeration of 0.80 vvm and an agitation rate of 300 rpm. The proposed microbial system is clean and effective for diosgenin production and thus more environmentally acceptable than the traditional acid hydrolysis.     

Immobilized cell reactors in mineralization of dicarboxylic acid solid waste

Dicarboxylic acid solid waste containing phthalic acid, malic acid, quinone, saturated and unsaturated dicarboxylic esters etc., are discharged in huge quantities during the crackdown of benzene over the catalyst vanadium at temperatures greater than 500 °C in a dicarboxylic acid manufacturing industry. Concern over the biological effects of these compounds underlines the necessity to treat this solid waste. The role of yeast Saccharomyces cerevisiae and anaerobic mixed bacterial cultures immobilized in activated carbon, in sequential two stage anoxic reactors, were investigated for the degradation of dicarboxylic acid solid waste (DASW). In the first stage, DASW was dissolved in water to yield a concentration of 0.5% w/v and was treated in yeast Saccharomyces cerevisiae immobilized reactor at an optimum residence time of 24 h. The yeast fermented samples were further treated in an upflow anaerobic reactor containing mixed culture immobilized in activated carbon at an Hydraulic Retention Time (HRT) of 0.2076 days at an hydraulic flow rate of 14.6×10⁻³ m³/day and Chemical Oxygen Demand (COD) loading rate of 4.3 kg/m³/day. The intermediates that were formed during the yeast fermentation and the anaerobic degradation of DASW were characterized by HPLC, proton NMR, C¹³ NMR and mass spectrometry.     

Synthesis of itaconic acid from agricultural waste using novel Aspergillus niveus

Abstract

Filamentous fungi from the genus Aspergillus are of high importance for the production of organic acids. Itaconic acid (IA) is considered as an important component for the production of synthetic fibers, resin, plastics, rubber, paints, coatings, adhesives, thickeners and binders. Aspergillus niveus MG183809 was isolated from the soil sample (wastewater unit) which was collected from Avadi, Chennai, India. In the present study, itaconic acid was successfully produced by isolated A. niveus by submerged batch fermentation. In the fermentation process, various low-cost substrates like corn starch, wheat flour and sweet potato were used for itaconic acid production. Further, the factor influencing parameters such as substrate concentration and incubation period were optimized. Maximum yield of itaconic acid (15.65?±?1.75?g/L) was achieved by using A. niveus from corn starch at a concentration of 120?g/L after 168?hr (pH 3.0). And also extraction of itaconic acid from the fermentation was performed with 91.96?±?1.57 degree of extraction.     

Production of oils and fats by oleaginous microorganisms with an emphasis given to the potential of the nonconventional yeast Yarrowia lipolytica

Recently, there has been a great upsurge of interest in studies related to several aspects of microbial lipid production, which is one of the top topics in relevant research fields due to the high demand of these fatty materials in food, medical, oleochemical and biofuel industries. Lipid accumulation by the so-called “oleaginous microorganisms” can generate more than 20% w/w of oil in dry biomass and is governed by a plethora of parameters, such as medium pH, incubation temperature, nutrient limitation and C/N (carbon/nitrogen) ratio, which drastically affect the lipid production bioprocess. Until now, considerable work has been undertaken to find the cheapest substrate to enable lipid fermentation by oleaginous microorganisms. This review principally details information regarding microbial lipids, suitable production conditions and focuses attention on using the yeast Yarrowia lipolytica to achieve these objectives. Lipid production by this yeast is discussed and the necessary conditions and suitable substrates are reviewed.     

Growth engineering of Propionibacterium freudenreichii shermanii for organic acids and other value-added products formation

Propionic acid production from glucose was studied using Propionibacterium freudenreichii shermanii. Conditions were optimized for high yields of propionic acid and total organic acids by sequential optimization of parameters like pH, inoculum age, inoculum volume and substrate concentration. Near-theoretical yield (0.54?±?0.023?g/g) was achieved for propionic acid with fermentation of 1% glucose using 20% (v/v) of 48?hr old P. shermanii at 30°C, pH maintained at 5.5. Total organic acid yield under these conditions was 0.74?±?0.06?g/g. The study resulted in achieving 98% and 95% theoretical yields of propionic acid and total organic acids, respectively. Under optimized conditions, along with organic acids, P. shermanii also produced vitamin B12 and trehalose intracellularly, showing its potential to be used as a cell factory.     

Viability and cellulose synthesizing ability of Gluconacetobacter xylinus cells under high-hydrostatic pressure

The effect of pressure on viability and the synthesis of bacterial cellulose (BC) by Gluconacetobacter xylinus ATCC53582 were investigated. G. xylinus was statically cultivated in a pressurized vessel under 0.1, 30, 60, and 100 MPa at 25°C for 6 days. G. xylinus cells remained viable and retained cellulose producing ability under all the conditions tested, though the production of cellulose decreased with increasing the pressure. The BCs produced at each pressure condition were analyzed by field emission scanning electron microscopy (FE-SEM) and Fourier Transform Infrared (FT-IR). FE-SEM revealed that the widths of BC fibers produced under high pressure decreased as compared with those produced under the atmospheric pressure. By FT-IR, all the BCs were found to be of Cellulose type I, as the same as typical native cellulose. Our findings evidently showed that G. xylinus possessed a piezotolerant (barotolerant) feature adapting to 100 MPa without losing its BC producing ability. This was the first attempt in synthesizing BC with G. xylinus under elevated pressure of 100 MPa, which corresponded to the deep sea at 10,000 m.     

Citric and gluconic acid production from fig by Aspergillus niger using solid-state fermentation

The production of citric and gluconic acids from fig by Aspergillus niger ATCC 10577 in solid-state fermentation was investigated. The maximal citric and gluconic acids concentration (64 and 490 g/kg dry figs, respectively), citric acid yield (8%), and gluconic acid yield (63%) were obtained at a moisture level of 75%, initial pH 7.0, temperature 30°C, and fermentation time in 15 days. However, the highest biomass dry weight (40 g/kg wet substrate) and sugar utilization (90%) were obtained in cultures grown at 35°C. The addition of 6% (w/w) methanol into substrate increased the concentration of citric and gluconic acid from 64 and 490 to 96 and 685 g/kg dry fig, respectively. Journal of Industrial Microbiology & Biotechnology (2000) 25, 298–304. Received 15 April 2000/ Accepted in revised form 11 August 2000     

Production of bacterial cellulose from Komagataeibacter saccharivorans strain BC1 isolated from rotten green grapes

Abstract

Bacterial cellulose (BC) is one of the prominent biopolymers that has been acquiring attention currently due to its distinctive properties and applications in various fields. The current work presents the isolation of Komagataeibacter saccharivorans strain BC1 isolated from rotten green grapes, followed by biochemical and genotypic characterization, which confirmed that the strain is capable of synthesizing cellulose. Further, production media was designed and certain variables such as carbon, nitrogen sources, pH, and temperature were optimized in order to obtain the maximum concentration of cellulose production. We found mannitol to be the ideal carbon source and yeast extract as the ideal nitrogen source with a highest BC dry yield of 1.81?±?0.25?g/100?mL at pH 5.76 for a week at 30?°C.The charcterization of pellicles by FTIR spectrum depicted similar functional groups present in synthesized BC as that of the commercial cellulose. X-ray diffraction revealed that BC showed 82% crystallinity. Surface morphology of the dried pellicle was studied by SEM image which showed that the BC surface was tightly packed with thin fibers with less porosity. Hence the study demonstrates that the isolates of K.saccharivorans could be used to produce a biopolymer in a short period of time using a modified production medium.     

Antifungal activity of crude extract produced by Bacillus sp. associated with entomopathogenic nematode from media formulated by six nitrogen sources with fructose against Penicillium expansum

A specific symbiotic Bacillus species isolated from a rhabditid entomopathogenic nematode, Rhabditis (Oscheius) sp. was found to produce a number of bioactive compounds. The present study was conducted to determine the effect of six different nitrogen sources in combination with fructose on the production of antifungal crude extract by Bacillus sp. against Penicillium expansum. The yield of crude extract and antifungal activity against the test fungi differed significantly when the nitrogen sources in the fermentation media were changed. The highest yield was recorded for beef extract plus fructose (921?mg/L). The antifungal activity was higher in yeast extract plus fructose [P. expansum (46.5?±?2.12?mm)], followed by beef extract. High performance liquid chromatography analysis of the crude antimicrobial substances revealed different peaks with different retention times indicating that they produced different compounds. When a carbon source was not included in the fermentation medium, the antimicrobial production was substantially reduced almost eight times. Carbon source in the fermentation medium plays a vital role in the production of antimicrobial substances. Yeast extract and fructose as nitrogen and carbon sources in the fermentation medium produced maximum antimicrobial activity.     

Enhancement of carotenoids and lipids production by oleaginous red yeast Sporidiobolus pararoseus KM281507

Bioconversion of biodiesel-derived crude glycerol into carotenoids and lipids was investigated by a microbial conversion of an oleaginous red yeast Sporidiobolus pararoseus KM281507. The methanol content in crude glycerol (0.5%, w/v) did not show a significant effect on biomass production by strain KM281507. However, demethanolized crude glycerol significantly supported the production of biomass (8.64?±?0.13?g/L), lipids (2.92?±?0.03?g/L), β-carotene (15.76?±?0.85?mg/L), and total carotenoids (33.67?±?1.28?mg/L). The optimal conditions suggested by central composite design were crude glycerol concentration (55.04?g/L), initial pH of medium (pH 5.63) and cultivation temperature (24.01°C). Under these conditions, the production of biomass, lipids, β-carotene, and total carotenoids were elevated up to 8.83?±?0.05, 4.00?±?0.06?g/L, 27.41?±?0.20, and 53.70?±?0.48?mg/L, respectively. Moreover, an addition of olive oil (0.5???2.0%) dramatically increased the production of biomass (14.47?±?0.15?g/L), lipids (6.40?±?0.09?g/L), β-carotene (54.43?±?0.95?mg/L), and total carotenoids (70.92?±?0.51?mg/L). The oleic acid content in lipids was also increased to 75.1% (w/w) of total fatty acids, indicating a good potential to be an alternative biodiesel feedstock. Meanwhile, the β-carotene content in total carotenoids was increased to 76.7% (w/w). Hence, strain KM281507 could be a good potential source of renewable biodiesel feedstock and natural carotenoids.