Jaggery: a novel substrate for pullulan production by Aureobasidium pullulans CFR-77

Strain improvement for enhanced erythritol production by Moniliella pollinis Mutant-58 using jaggery as a cost-effective substrate

Erythritol has been produced by various microorganisms including Yarrowia, Moniliella, Aureobasidium, and Candida strains. Due to its relatively high price, erythritol sweetener is used lesser than other polyols despite having many advantages. Therefore, in this study, Moniliella pollinis strain was improved for erythritol production by chemical mutagenesis and subsequently screening for cost-effective carbon sources for the enhanced erythritol yield. M. pollinis was subjected to N-methyl N-nitro N-nitroso guanidine (NTG), ethyl methyl sulfonate (EMS), and UV mutagenesis for improved erythritol production. The fmutant strains were evaluated for enhanced erythritol production medium optimization by using different carbon substrates at the shake flask level. To enhance the production of erythritol and statistical media, optimization was carried out using a central composite design (CCD). Among 198 isolated mutants, Mutant-58 strain generated by EMS mutagenesis was selected for further assessment. The Mutant-58 strain showed significant morphological changes as compared to the parent strain. Furthermore, statistically optimized media composition resulted in the higher production of erythritol (91.2 ± 3.4 g/L) with a yield of 40.7 ± 3.4 % in shake flask experiments. The optimized medium composition for erythritol production constitutes (g/L) 225 jaggery, 4.4 yeast extract (YE), 4.4 KH2PO4, 0.31 MgSO4, and pH 5.5. The present study demonstrated strain improvement, media, and process optimization resulting in a 30% increase in the erythritol production in the Mutant-58 as compared to the parent strain. This is also the first instance where jaggery has been used as a cost-effective carbon source alternative to glucose for industrial-scale erythritol production.

Downstream processing and structural confirmation of pullulan - A comprehensive review

Pullulan is a microbial polymer, commercially produced from Aureobasidium pullulans. Downstream processing of pullulan involves a multi-stage process which should be efficient, safe and reproducible. In liquid-liquid separations, firstly cell free extract is separated. Cell biomass can be separated after fermentation either by centrifugation or filtration. Due to practically insolubility of pullulan in organic solvents, ethanol and isopropanol are the most commonly used organic solvents for its recovery. Pullulan can also be purified by chromatographic techniques, but these are not cost effective for the purification of pullulan. Efficient aqueous two-phase system can be used for the purification of pullulan. The current review describes the methods and perspectives used for solid-liquid separation, liquid-liquid separations and finishing steps for the recovery of pullulan. Techniques used to determine the structural attributes of pullulan have also been highlighted.

Evaluation of Some Agro-Industrial Wastes as Fermentation Medium for Pullulan Production by Aureobasidium pullulans AZ-6

Agro-industrial wastes are rich sources of some nutrients. Thus, utilization of wastes seems to be ecologically sound and economically advantageous. The aim of this work was to investigate the potential usage of various agro-industrial wastes as fermentation medium for pullulan production by a domestic strain; Aureobasidium pullulans AZ-6. In this study, different agro-industrial wastes; various citrus peels, grape pomace, the hydrolysates of hazelnut and chestnut shells, sugarcane molasses residue, dried and fresh hazelnut husks and pumpkin peel, were used as fermentation media without adding any extra nutritional component for pullulan production by A. pullulans AZ-6. As a result, among the tested media, the maximum pullulan concentration was obtained as 33.59 gL^-1 using the sugarcane molasses residue, and followed by the corresponding value of 30.02 gL^-1 obtained in the dried hazelnut husk hydrolysate medium. Therefore, the usage of agro-industrial wastes as fermentation media is considered to make pullulan production cost effective. In addition, waste treatment from this aspect solves a relevant environmental problem. In this study, sugarcane molasses residue and dried hazelnut husk hydrolysate were used directly as fermentation media for pullulan production for the first time. Pullulan production from sugarcane molasses residue and dried hazelnut husk hydrolysate media might be a promising substrate for economical point of view.

Biopolymer production by Aureobasidium mangrovei SARA-138H and its potential for oil recovery enhancement

The world economy depends heavily on crude oil. With a conventional oil recovery process, only one-third of crude oil is extracted. Various technologies have been developed to maximize the recovery of oil resources from natural reservoirs. Polymer technology has been used in many oil fields around the world. The biopolymer pullulan, produced by some Aureobasidium species, has been used in many industrial applications, but no research has been conducted regarding its use in the microbial enhancement of oil recovery (MEOR). Here, we investigate the potential of pullulan produced by newly isolated species Aureobasidium mangrovei SARA-138H for enhancement of oil recovery. Our results indicate that under optimized conditions, that is, sucrose as the carbon source in the medium, a pH of 9, incubation at 25 °C, and 250 rpm agitation, the fungus was able to produce 10 g/L of pullulan. The maximum viscosity achieved under these conditions was 318 cP after 15 days of incubation. Pullulan solution (10 g/L) showed the ability to recover 36.7% of heavy crude oil after 34.2% of secondary oil recovery. However, diluted pullulan in brine at the ratio (1:1) resulted in the recovery of 20.23% of oil from the residual oil in the core after 22.6% of secondary oil recovery. A 20-day injectivity test revealed that pullulan passed smoothly through the core, causing no blockage. It was concluded that pullulan from A. mangrovei SARA-138H was able to increase oil recovery to a degree comparable to that achieved with many polymers used in oil fields around the world. KEY POINTS: • First report of biopolymer "pullulan" from A. mangrovie. • Optimum conditions for pullulan production were obtained. • Pullulan recovered 36.7% of heavy oil from residual oil in place, with good injectivity.

An integrated valorization of industrial waste of eggplant: Simultaneous recovery of pectin, phenolics and sequential production of pullulan

Based on a bio-refinery concept, the valorization of eggplant peel wastes (EPW) in the production of multiple value-added products was aimed. The acid-free extraction process was applied in the simultaneous recovery of pectin and phenolic compounds. The extraction variables were optimized by response surface methodology using a Box-Behnken design and the maximum yield of pectin (26.1%) and phenolic compounds (20.2%) was obtained in the extraction temperature of 90 °C, time of 90 min and liquid/solid ratio of 40 mL/g. After recovery of pectin and phenolic compounds from EPW, the solid leftovers were enzymatic hydrolyzed and the hydrolysates were used as a carbon source in the microbial production of pullulan by Aureobasidium pullulans. The produced pectin and pullulan were characterized through the chemical and structural features. The results of FT-IR and H-NMR analysis approved the predominant presence of these two polysaccharides in the isolated samples. On the other hand, the antioxidant activity of the recovered phenolic compounds extract was evaluated by DPPH and ABTS radical scavenging activity and reducing power assay.

Bacterial Cellulose and Pullulan from Simple and Low Cost Production Media

In this study, the production rate of both water-insoluble EPS, bacterial cellulose, and water-soluble EPS, P, was improved through сultivation of their producers on a nutrient media containing industrial wastes, and their material properties were analyzed. The growth rate and productivity of Gluconoacetobacter xylinus C3 strain on media with industrial wastes was investigated. An optimal nutrient medium based on molasses was selected for the bacterial cellulose producer. The nutrient medium contains 2% molasses, 1% yeast extract and peptone in a 1: 1 ratio, 0.3% sodium hydrogen phosphate, 0.1% citric acid and 1% ethanol. Cultivation of Gluconoacetobacter xylinus C3 strain on this medium for 7 days at 25–30 °С ensures its high productivity – 8.21 g/L. The composition of the optimized medium with molasses provides high mechanical properties (tensile strength – 37.12 MPa and relative elongation at break – 3.28%) of bacterial cellulose and does not affect the polymer microfibrillar structure. A modified Czapek-Dox medium with 10% molasses and 1% peptone is preferable for the exopolysaccharide accumulation by A. pullulans C8 strain. The optimized media has an advantage over the traditionally used media in terms of the efficiency of exopolysaccharide accumulation and cost reduction. The pullulan yield in media was 10.08 g/l, that is 1.5 times higher than in a standard Czapek-Dox medium. The surface morphology and microstructure of the pullulan samples obtained on different media showed minor changes. Therefore, the replacement of carbon source for molasses in a Czapek-Dox media for pullulan production did not alter the polymer content and viscosity.

Pullulan production from synthetic medium by a new mutant of Aureobasidium pullulans

Pullulan with different molecular-weight could be applied in various fields. A UV-induced mutagenesis Aureobasidium pullulans UVMU6-1 was obtained from the strain A. pullulans CGMCC3.933 for the production of low-molecular-weight pullulan. First, the obtained polysaccharide from A. pullulans UVMU6-1 was purified and identified to be pullulan with thin-layer chromatography, Fourier transform infrared, and nuclear magnetic resonance. Then, culture medium and conditions for this strain were optimized by flask fermentation. Based on the optimized medium and culture conditions (pH 4, addition of 4 g/L Tween 80 for 96 hr of cultivation), continuously fermentation was performed. The highest pullulan production and dry biomass was 109 and 125 g/L after fermentation for 114 hr, respectively. The average productivity was about 1 g/L/hr, which was intensively higher than the previous reported. This study would lay foundations for the industrial production of pullulan.

Low-melanin containing pullulan production from sugarcane bagasse hydrolysate by Aureobasidium pullulans in fermentations assisted by light-emitting diode

Pullulan is a polymer produced by Aureobasidium pullulans and the main bottleneck for its industrial production is the presence of melanin pigment. In this study, light-emitting diodes (LEDs) of different wavelengths were used to assist the fermentation process aiming to produce low-melanin containing pullulan by wild strain of A. pullulans LB83 with different carbon sources. Under white light using glucose-based medium, 11.75g.L^-1 of pullulan with high melanin content (45.70UA_540nm.g^-1) was obtained, this production improved in process assisted by blue LED light, that resulted in 15.77g.L^-1 of pullulan with reduced content of melanin (4.46UA_540nm.g^-1). By using sugarcane bagasse (SCB) hydrolysate as carbon source, similar concentration of pullulan (about 20g.L^-1) was achieved using white and blue LED lights, with lower melanin contents in last. Use of LED light was found as a promising approach to assist biotechnological process for low-melanin containing pullulan production.

Plant Food Residues as a Source of Nutraceuticals and Functional Foods

This chapter describes the use of different plant and vegetable food residues as nutraceuticals and functional foods. Different nutraceuticals are mentioned and explained. Their uses are well addressed along with their disease management and their action as nutraceutical delivery vehicles.

Statistical optimization of process parameters for exopolysaccharide production by Aureobasidium pullulans using sweet potato based medium

Statistical experimental designs were applied to optimize the fermentation medium for exopolysaccharide (EPS) production. Plackett–Burman design was applied to identify the significance of seven medium variables, in which sweet potato and yeast extract were found to be the significant variables for EPS production. Central composite design was applied to evaluate the optimum condition of the selected variables. Maximum EPS production of 9.3 g/L was obtained with the predicted optimal level of sweet potato 10 %, yeast extract 0.75 %, 5.5 pH, and time 100 h. The determined (R²) value was 0.97, indicating a good fitted model for EPS production. Results of this study showed that sweet potato can be utilized as a low-cost effective substrate for pullulan production in submerged fermentation.

The mechanism of improved pullulan production by nitrogen limitation in batch culture of Aureobasidium pullulans

Batch culture of Aureobasidium pullulans CCTCC M 2012259 for pullulan production at different concentrations of ammonium sulfate and yeast extract was investigated. Increased pullulan production was obtained under nitrogen-limiting conditions, as compared to that without nitrogen limitation. The mechanism of nitrogen limitation favoring to pullulan overproduction was revealed by determining the activity as well as gene expression of key enzymes, and energy supply for pullulan biosynthesis. Results indicated that nitrogen limitation increased the activities of α-phosphoglucose mutase and glucosyltransferase, up-regulated the transcriptional levels of pgm1 and fks genes, and supplied more ATP intracellularly, which were propitious to further pullulan biosynthesis. The economic analysis of batch pullulan production indicated that nitrogen limitation could reduce more than one third of the cost of raw materials when glucose was supplemented to a total concentration of 70 g/L. This study also helps to understand the mechanism of other polysaccharide overproduction by nitrogen limitation.

Efficient production of pullulan using rice hull hydrolysate by adaptive laboratory evolution of Aureobasidium pullulans

Pullulan production by Aureobasidium pullulans CCTCC M 2012259 using rice hull hydrolysate as the carbon source was conducted. The acetic acid in the hydrolysate was demonstrated to exert a negative effect on pullulan biosynthesis. Instead of employing expensive methods to remove acetic acid from the hydrolysate, a mutant A. pullulans ARH-1 was isolated following 20 cycles of adaptive laboratory evolution of the parental strain on medium containing acetic acid. The maximum pullulan production achieved by the adapted mutant at 48 h using the hydrolysate of untreated rice hull was 22.2 g L(-1), while that obtained by the parental strain at 60 h was 15.6 g L(-1). The assay of key enzymes associated with pullulan biosynthesis revealed that acetic acid inhibited enzyme activity rather than suppressing enzyme synthesis. These results demonstrated that adaptive evolution highly improved the efficiency of pullulan production by A. pullulans using the hydrolysate of untreated rice hull.

Influence of controlled pH on the activity of UDPG-pyrophosphorylase in Aureobasidium pullulans

UDPG-pyrophosphorylase is the key enzyme involved in pullulan biosynthesis and pullulan production by Aureobasidium pullulans. In this study, effect of controlled pH on fermentation time, pullulan production, biomass, and UDPG-pyrophosphorylase activity was investigated. Pullulan yield increased to reach a maximum within 4 days, and maximum UDPG-pyrophosphorylase activity was observed at day 3, while the biomass continued to increase until the end of the experimental period. The A. pullulans isolated from sea mud grew well at relatively low pH. UDPG-pyrophosphorylase activity was affected by the controlled pH and reached a maximum at pH 5.5. Results indicated that UDPG-pyrophosphorylase activity was highly correlated with controlled pH and pullulan biosynthesis rate.

Deoiledjatropha seed cake is a useful nutrient for pullulan production

Background

Ever increasing demand for fossil fuels is a major factor for rapid depletion of these non-renewable energy resources, which has enhanced the interest of finding out alternative sources of energy. In recent years jatropha seed oil has been used extensively for production of bio-diesel and has shown significant potential to replace petroleum fuels at least partially. De-oiled jatropha seed cake (DOJSC) which comprises of approximately 55 to 65% of the biomass is a byproduct of bio-diesel industry. DOJSC contains toxic components like phorbol esters which restricts its utilization as animal feed. Thus along with the enhancement of biodiesel production from jatropha, there is an associated problem of handling this toxic byproduct. Utilization of DOJSC as a feed stock for production of biochemicals may be an attractive solution to the problem.

Pullulan is an industrially important polysaccharide with several potential applications in food, pharmaceuticals and cosmetic industries. However, the major bottleneck for commercial utilization of pullulan is its high cost. A cost effective process for pullulan production may be developed using DOJSC as sole nutrient source which will in turn also help in utilization of the byproduct of bio-diesel industry.

Results

In the present study, DOJSC has been used as a nutrient for production of pullulan, in place of conventional nutrients like yeast extract and peptone. Process optimization was done in shake flasks, and under optimized conditions (8% DOJSC, 15% dextrose, 28°C temperature, 200 rpm, 5% inoculum, 6.0 pH) 83.98 g/L pullulan was obtained. The process was further validated in a 5 L laboratory scale fermenter.

Conclusion

This is the first report of using DOJSC as nutrient for production of an exopolysaccharide. Successful use of DOJSC as nutrient will help in finding significant application of this toxic byproduct of biodiesel industry. This in turn also have a significant impact on cost reduction and may lead to development of a cost effective green technology for pullulan production.

Production of exopolysaccharides by Agrobacterium sp. CFR-24 using coconut water - a byproduct of food industry

AIMS

The work is intended to explore the suitability of underutilized coconut water (a byproduct of food industry) for the production of exopolysaccharides (EPS) by Agrobacterium sp. CFR 24.

METHODS AND RESULTS

Besides checking the suitability of coconut water for the production of water-soluble (WS) and water-insoluble (WIS) EPS, certain fermentation parameters, such as initial pH, incubation period and kinetics of EPS production were investigated. The coconut water medium was found to support the production of both types of EPS. The optimal initial pH and temperature was found to be 6.0 and 30 degrees C, respectively. In shake flask (150 rev min(-1)) studies, high-cell density inoculum resulted in the production of 11.50 g l(-1) of WIS-EPS and 4.01 g l(-1) WS-EPS after 72 and 96 h of fermentation, respectively.

CONCLUSIONS

Coconut water was found suitable for the production of microbial EPS by Agrobacterium sp. CFR 24 strain. Under optimum conditions, it produced a good amount of WIS-EPS, which is comparable with that of the sucrose medium (11 g l(-1)).

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report on the use of coconut water as a fermentation medium for the production of any microbial EPS. Besides producing value-added products, use of this food industry byproduct, which is often being drained out, can significantly reduce the problem of environmental pollution.