Use of sugarcane bagasse as biomaterial for cell immobilization for xylitol production

Sugarcane bagasse: a biomass sufficiently applied for improving global energy, environment and economic sustainability

Sugarcane (Saccharum officinarum) bagasse (SCB) is a biomass of agricultural waste obtained from sugarcane processing that has been found in abundance globally. Due to its abundance in nature, researchers have been harnessing this biomass for numerous applications such as in energy and environmental sustainability. However, before it could be optimally utilised, it has to be pre-treated using available methods. Different pre-treatment methods were reviewed for SCB, both alkaline and alkali-acid process reveal efficient and successful approaches for obtaining higher glucose production from hydrolysis. Procedures for hydrolysis were evaluated, and results indicate that pre-treated SCB was susceptible to acid and enzymatic hydrolysis as > 80% glucose yield was obtained in both cases. The SCB could achieve a bio-ethanol (a biofuel) yield of > 0.2 g/g at optimal conditions and xylitol (a bio-product) yield at > 0.4 g/g in most cases. Thermochemical processing of SCB also gave excellent biofuel yields. The plethora of products obtained in this regard have been catalogued and elucidated extensively. As found in this study, the SCB could be used in diverse applications such as adsorbent, ion exchange resin, briquettes, ceramics, concrete, cement and polymer composites. Consequently, the SCB is a biomass with great potential to meet global energy demand and encourage environmental sustainability.

Supporting role of lignin in immobilization of yeast on sugarcane bagasse for continuous pectinase production

BACKGROUND

Lignocellulosic wastes are pretreated prior to their utilization in fermentation processes. Such pretreatment also alters the topological features of the substrates, and therefore the suitability of pretreated waste as immobilization matrix for microbial cells needs investigation.

RESULTS

In this study, the effect of chemical pretreatment of sugarcane bagasse (SB) for its subsequent utilization as a matrix to immobilize a pectinolytic yeast, Geotrichum candidum AA15, was evaluated using cell retention, concentration of immobilized cells, immobilization efficiency, scanning electron microscopy and Fourier transform infrared spectroscopy of the substrate and pectinase titers obtained after recycling. The results revealed that untreated SB is more efficient for immobilization with higher values of cell retention and pectinase productivity (99.78%) retained for up to six production cycles. It was deduced that removal of lignin by pretreatment negatively influenced the ability of SB to support cell adhesion, as lignin acts as a sealing agent that provides strength to the substrate.

CONCLUSIONS

The strategy of utilizing SB as immobilization matrix was found effective at the laboratory scale as it improved pectinase production and may be investigated further for large-scale and cost-effective production. © 2020 Society of Chemical Industry.

Cellulosic and hemicellulosic fractions of sugarcane bagasse: Potential, challenges and future perspective

Sugarcane bagasse is a rich source of cellulose (32-45%), hemicellulose (20-32%) and lignin (17-32%), 1.0-9.0% ash and some extractives. Huge amount of the generation of sugarcane bagasse has been a great challenge to industries and environment at global level for many years. Though cellulosic and hemicellulosic fractions in bagasse makes it a potential raw substrate for the production of value-added products at large scale, the presence of lignin hampers its saccharification which further leads to low yields of the value-added products. Therefore, an appropriate pretreatment strategy is of utmost importance that effectively solubilizes the lignin that exposes cellulose and hemicellulose for enzymatic action. Pretreatment also reduces the biomass recalcitrance i.e., cellulose crystallinity, structural complexity of cell wall and lignification for its effective utilization in biorefinery. Sugarcane bagasse served as nutrient medium for the cultivation of diverse microorganisms for the production of industrially important metabolites including enzymes, reducing sugars, prebiotic, organic acids and biofuels. Sugarcane bagasse has been utilized in the generation of electricity, syngas and as biosorbant in the bioremediation of heavy metals. Furthermore, the ash generated from bagasse is an excellent source for the synthesis of high strength and light weight bricks and tiles. Present review describes the utility of sugarcane bagasse as sustainable and renewable lignocellulosic substrate for the production of industrially important multifarious value-added products.

Isolation of Efficient Metal-Binding Bacteria from Boreal Peat Soils and Development of Microbial Biosorbents for Improved Nickel Scavenging

Boreal peatlands with low iron availability are a potential, but rarely studied, source for the isolation of bacteria for applications in metal sorption. The present research focused on the isolation and identification of Actinobacteria from northern Finland, which can produce siderophores for metal capture. The 16S rDNA analysis showed that isolated strains belonged to Firmicutes (Bacillus sp.) and Actinobacteria (Microbacterium sp.). The culture most efficiently producing siderophores in the widest array of the media was identified as Microbacterium sp. The most appropriate media for siderophore production by the Microbacterium strain were those prepared with glucose supplemented with asparagine or glutamic acid, and those prepared with glycerol or fructose supplemented with glutamic acid. The microorganism obtained and its siderophores were used to develop Sphagnum moss-based hybrid biosorbents. It was showed that the hybrid sorbent could bind nickel ions and that the nickel removal was enhanced by the presence of siderophores. Bacterial cells did not have a significant effect on sorption efficiency compared to the use of siderophores alone. The microbial biosorbent could be applied in the final effluent treatment stage for wastewater with low metal concentrations.

Development of a Novel Spawn (Block Spawn) of an Edible Mushroom, Pleurotus ostreatus, in Liquid Culture and its Cultivation Evaluation

Mushroom cultivation has gained increased attention in recent years. Currently, only four types of spawn, including sawdust spawn, grain spawn, liquid spawn, and stick spawn, are commonly available for mushroom cultivation. This limited spawn diversity has led to difficulty in selecting suitable inoculum materials in some cultivation. In this study, three small blocks of lignocellulosic agro-wastes and one block of a synthetic matrix were prepared as support for growing Pleurotus ostreatus in liquid medium. Mycelium-adsorbed blocks were then evaluated for their potential as block spawn for fructification. Our results indicated that the edible fungus was adsorbed and abundantly grew internally and externally on loofah sponge and synthetic polyurethane foam (PUF) supports and also has the ability to attach and grow on the surface of sugarcane bagasse and corncob supports. The mycelia of P. ostreatus adhered on corncob exhibited the highest metabolic activity, while those on the PUF showed the least activity. Mycelial extension rates of block spawns made of agro-waste materials were comparable to that of sawdust spawn, but the block spawn of PUF showed a significantly lower rate. No significant differences in cropping time and yield were observed among cultivations between experimental block spawns and sawdust spawns. Moreover, the corncob block spawn maintained its fruiting potential during an examined period of 6-month storage. The developed block spawn could be practically applied in mushroom cultivation.

Predominant Yeasts During Artisanal Mezcal Fermentation and Their Capacity to Ferment Maguey Juice

Artisanal mezcal is produced by the natural fermentation of maguey juice, which frequently results in a process that becomes stuck or is sluggish. Using selected indigenous starter inoculums of Saccharomyces and non-Saccharomyces yeasts is considered beneficial in overcoming these problems and thereby preserving the essence of the artisanal process. In this work, three hundred and four yeast isolates were recovered from 17 distilleries and then grouped by the ARDRA analysis, their restriction profiles were clustered in 15 groups. Four of them included 90% of all isolates, and these were identified using the sequence of the D1/D2 domain of the large-subunit rDNA. Pichia kudriavzevii, Pichia manshurica, Saccharomyces cerevisiae, and Kluyveromyces marxianus were detected as predominant species. Both species belonging to the Pichia genus were detected in 88% of the distilleries, followed by S. cerevisiae (70%) and K. marxianus (50%). In order to evaluate the fermentative capacity, one strain of each species was assessed in a pure and mixed culture in two culture media, filtered maguey juice (MJ) and maguey juice including its bagasse (MJB). Findings demonstrated that non-Saccharomyces yeast presented better growth than that of S. cerevisiae. K. marxianus PA16 was more efficient for ethanol production than S. cerevisiae DI14. It produced 32 g/L of ethanol with a yield of 0.47 g/g and efficient of 90%. While, P. kudriavzevii produced more ethyl acetate (280 mg/L) than the others species. All fermentations were characterized by the presence of isobutyl and isoamyl alcohol. The presence of K. marxianus in a mixed culture, improved the ethanol production and volatile compounds increased using co-cultures.

Production of xylitol and bio-detoxification of cocoa pod husk hemicellulose hydrolysate by Candida boidinii XM02G

The use of cocoa pod husk hemicellulose hydrolysate (CPHHH) was evaluated for the production of xylitol by Candida boidinii XM02G yeast isolated from soil of cocoa-growing areas and decaying bark, as an alternative means of reusing this type of waste. Xylitol was obtained in concentrations of 11.34 g.L^-1, corresponding to a yield (Y_p/s) of 0.52 g.g^-1 with a fermentation efficiency (ε) of 56.6%. The yeast was tolerant to inhibitor compounds present in CPHHH without detoxification in different concentration factors, and was able to tolerate phenolic compounds at approximately 6 g.L^-1. The yeast was also able to metabolize more than 99% (p/v) of furfural and hydroxymethylfurfural present in the non-detoxified CPHHH without extension of the cell-growth lag phase, showing the potential of this microorganism for the production of xylitol. The fermentation of cocoa pod husk hydrolysates appears to provide an alternative use which may reduce the impact generated by incorrect disposal of this waste.

Acidic and enzymatic saccharification of waste agricultural biomass for biotechnological production of xylitol

Background

The plant biomass and agro-industrial wastes show great potential for their use as attractive low cost substrates in biotechnological processes. Wheat straw and corn cob as hemicellulosic substrates were acid hydrolyzed and enzymatically saccharified for high xylose production. The hydrolysate was concentrated and fermented by using Saccharomyces cerevisiae and Kluyveromyces for production of xylitol.

Results

Acid hydrolysis of wheat straw and corn cob in combination with enzymatic hydrolysis showed great potential for production of free sugars from these substrates. Kluyveromyces produced maximum xylitol from acid treated wheat straw residues with enzymatic saccharification. The percentage xylitol yield was 89.807 g/L and volumetric productivity of 0.019 g/L/h. Kluyveromyces also produced maximum xylitol from corn cob acid hydrolyzed liquor with xylitol yield 87.716 g/L and volumetric productivity 0.018 g/L/h.

Conclusion

Plant and agro-industrial biomass can be used as a carbohydrate source for the production of xylitol and ethanol after microbial fermentation. This study revealed that wheat straw acid and enzyme hydrolyzed residue proved to be best raw material for production of xylitol with S. cerevisiae. The xylitol produced can be utilized in pharmaceuticals after purification on industrial scale as pharmaceutical purposes.

Photocatalytic degradation of pharmaceutical wastes by alginate supported TiO2 nanoparticles in packed bed photo reactor (PBPR)

In recent years deposal of pharmaceutical wastes has become a major problem globally. Therefore, it is necessary to removes pharmaceutical waste from the municipal as well as industrial effluents before its discharge. The convectional wastewater and biological treatments are generally failed to separate different drugs from wastewater streams. Thus, heterogeneous photocatalysis process becomes lucrative method for reduction of detrimental effects of pharmaceutical compounds. The main disadvantage of the process is the reuse or recycle of photocatalysis is a tedious job. In this work, the degradation of aqueous solution of chlorhexidine digluconate (CHD), an antibiotic drug, by heterogeneous photocatalysis was study using supported TiO2 nanoparticle. The major concern of this study is to bring down the limitations of suspension mode heterogeneous photocatalysis by implementation of immobilized TiO2 with help of calcium alginate beads. The alginate supported catalyst beads was characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDAX) as well as the characteristic crystalline forms of TiO2 nanoparticle was confirmed by XRD. The degradation efficiency of TiO2 impregnated alginate beads (TIAB) was compared with the performance of free TiO2 suspension. Although, the degradation efficiency was reduced considerably using TIAB but the recycle and reuse of catalyst was increased quite appreciably. The kinetic parameters related to this work have also been measure. Moreover, to study the susceptibility of the present system photocatalysis of other three drugs ibuprofen (IBP), atenolol (ATL) and carbamazepine (CBZ) has been carried out using immobilized TiO2. The continuous mode operation in PBPR has ensured the applicability of alginate beads along with TiO2 in wastewater treatment. The variation of residence time has significant impact on the performance of PBPR.

Xylitol production by genetically engineered Trichoderma reesei strains using barley straw as feedstock

Xylitol, a naturally occurring five-carbon sugar alcohol derived from D-xylose, is currently in high demand by industries. Trichoderma reesei, a prolific industrial cellulase and hemicellulase producing fungus, is able to selectively use D-xylose from hemicelluloses for xylitol production. The xylitol production by T. reesei can be enhanced by genetic engineering of blocking further xylitol metabolism in the D-xylose pathway. We have used two different T. reesei strains which are impaired in the further metabolism of xylitol including a single mutant in which the xylitol dehydrogenase gene was deleted (∆xdh1) and a double mutant where additionally L-arabinitol-4-dehydrogenase, an enzyme which can partially compensate for xylitol dehydrogenase function, was deleted (∆lad1∆xdh1). Barely straw was first pretreated using NaOH and Organosolv pretreatment methods. The highest xylitol production of 6.1 and 13.22 g/L was obtained using medium supplemented with 2 % Organosolv-pretreated barley straw and 2 % D-xylose by the ∆xdh1 and ∆lad1∆xdh1 strains, respectively.

Xylitol production from corncob hydrolysate using polyurethane foam with immobilized Candida tropicalis

Polyurethane foam (PUF) was used as a carrier for Candida tropicalis (C. tropicalis) in the multi-batches fermentation of xylitol from xylose-containing corncob hemicellulose hydrolysate. After washing and sterilization, PUF (density of 320 kgm(-3), specific surface area of 1.5-2.0 × 10(5) m(2) m(-3), average porosity of 95%, pore diameter of 0.03 mm and cubic length of 5mm) was mixed with the culture medium at appropriate proportion followed by the inoculation. The fermentation parameters such as initial cell concentration, PUF dosage, pH value and temperature were controlled to study the effects on xylitol fermentation. In the 21-day durability tests, the optimal xylitol yield and volumetric productivity reached to 71.2% and 2.10 gL(-1)h(-1) respectively. Moreover, the average xylitol yield and volumetric productivity were 66.3% and 1.90 gL(-1)h(-1) for ten batchwise operations. The current research demonstrated that the PUF immobilization could serve as an efficient method for improving the cells vitality and enzyme reactivity in the continuous operation of fermentation.

Ethanol production from sweet sorghum juice in repeated-batch fermentation by Saccharomyces cerevisiae immobilized on corncob

Ethanol fermentation from sweet sorghum juice containing 240 g/l of total sugar by Saccharomyces cerevisiae TISTR 5048 and S. cerevisiae NP 01 immobilized on low-cost support materials, corncob pieces, was investigated. In batch fermentation, S. cerevisiae TISTR 5048 immobilized on 6 × 6 × 6 mm(3) corncobs gave higher ethanol production than those immobilized on 12 × 12 × 12 mm(3) corncobs in terms of ethanol concentration (P), yield (Y ( p/s )) and productivity (Q ( p )) with the values of 102.39 ± 1.11 g/l, 0.48 ± 0.01 and 2.13 ± 0.02 g/l h, respectively. In repeated-batch fermentation, the yeasts immobilized on the 6 × 6 × 6 mm(3) corncobs could be used at least eight successive cycles with the average P, Y ( p/s ) and Q ( p ) of 97.19 ± 5.02 g/l, 0.48 ± 0.02 and 2.02 ± 0.11 g/l h, respectively. Under the same immobilization and repeated-batch fermentation conditions, P (90.75 ± 3.05 g/l) and Q ( p ) (1.89 ± 0.06 g/l h) obtained from S. cerevisiae NP 01 were significantly lower than those from S. cerevisiae TISTR 5048 (P < 0.05), while Y ( p/s ) from both strains were not different. S. cerevisiae TISTR 5048 immobilized on the corncobs also gave significantly higher P, Y ( p/s ) and Q ( p ) than those immobilized on calcium alginate beads (P < 0.05).

Ethanol production from sugar beet molasses by S. cerevisiae entrapped in an alginate-maize stem ground tissue matrix

A new alginate-maize stem ground tissue matrix was developed as a Saccharomyces cerevisiae carrier for ethanol fermentation from sugar beet molasses. There were several fermentation procedures in the present study: using free cells and alginate-entrapped cells with and without maize stem ground tissue supplementation (F; F+C; AB; AB+C), and using a new combined alginate-maize stem ground tissue carrier (ABC). It was found that addition of maize stem ground tissue meal (C), with honeycomb configuration, provided high surface areas for cell attachment and biofilm growth, and also increased alginate matrix porosity, enabling better mass transfer characteristic, better physical strength and stability of beads. The highest values of process parameters were obtained in the case of new carrier (ABC): the ethanol concentration of 60.36 g/l, percentage of the theoretical ethanol yield of 96.56%, ethanol yield of 0.493 g/g and the volumetric ethanol productivity of 2.51 g/lh. The medium supplementation with maize stem ground tissue significantly decreased acetaldehyde and acetic acid content, did not affect fusel alcohol and ethylacetate content of the distillate.

Ethanol production using immobilized Saccharomyces cerevisiae in lyophilized cellulose gel

A new lyophilization technique was used for immobilization of Saccharomyces cerevisiae cells in hydroxyethylcellulose (HEC) gels. The suitability of the lyophilized HEC gels to serve as immobilization matrices for the yeast cells was assessed by calculating the immobilization efficiency and the cell retention in three consecutive batches, each in duration of 72 h. Throughout the repeated batch fermentation, the immobilization efficiency was almost constant with an average value of 0.92 (12-216 h). The maximum value of cell retention was 0.24 g immobilized cells/g gel. Both parameters indicated that lyophilized gels are stable and capable of retaining the immobilized yeast cells. Showing the yeast cells propagation within the polymeric matrix, the scanning electron microscope images also confirmed that the lyophilization technique for immobilization of S. cerevisiae cells in the HEC gels was successful. The activity of the immobilized yeast cells was demonstrated by their capacity to convert glucose to ethanol. Ethanol yield of 0.40, 0.43 and 0.30 g ethanol/g glucose corresponding to 79%, 84% and 60% of the theoretical yield was attained in the first, second and third batches, respectively. The cell leakage was less than 10% of the average concentration of the immobilized cells.

Ethanol production by fermentation using immobilized cells of Saccharomyces cerevisiae in cashew apple bagasse

In this work, cashew apple bagasse (CAB) was used for Saccharomyces cerevisiae immobilization. The support was prepared through a treatment with a solution of 3% HCl, and delignification with 2% NaOH was also conducted. Optical micrographs showed that high populations of yeast cells adhered to pre-treated CAB surface. Ten consecutive fermentations of cashew apple juice for ethanol production were carried out using immobilized yeasts. High ethanol productivity was observed from the third fermentation assay until the tenth fermentation. Ethanol concentrations (about 19.82-37.83 g L(-1) in average value) and ethanol productivities (about 3.30-6.31 g L(-1) h(-1)) were high and stable, and residual sugar concentrations were low in almost all fermentations (around 3.00 g L(-1)) with conversions ranging from 44.80% to 96.50%, showing efficiency (85.30-98.52%) and operational stability of the biocatalyst for ethanol fermentation. Results showed that cashew apple bagasse is an efficient support for cell immobilization aiming at ethanol production.

Use of Saccharum spontaneum (wild sugarcane) as biomaterial for cell immobilization and modulated ethanol production by thermotolerant Saccharomyces cerevisiae VS3

Saccharum spontaneum is a wasteland weed consists of 45.10+/-0.35% cellulose and 22.75+/-0.28% of hemicellulose on dry solid (DS) basis. Aqueous ammonia delignified S. spontaneum yielded total reducing sugars, 53.91+/-0.44 g/L (539.10+/-0.55 mg/g of substrate) with a hydrolytic efficiency of 77.85+/-0.45%. The enzymes required for hydrolysis were prepared from culture supernatants of Aspergillus oryzae MTCC 1846. A maximum of 0.85+/-0.07 IU/mL of filter paperase (FPase), 1.25+/-0.04 IU/mL of carboxy methyl cellulase (CMCase) and 55.56+/-0.52 IU/mL of xylanase activity was obtained after 7 days of incubation at 28+/-0.5 degrees C using delignified S. spontaneum as carbon source under submerged fermentation conditions. Enzymatic hydrolysate of S. spontaneum was then tested for ethanol production under batch and repeated batch production system using "in-situ" entrapped Saccharomyces cerevisiae VS3 cells in S. spontaneum stalks (1 cm x 1 cm) size. Immobilization was confirmed by the scanning electron microscopy (SEM). Batch fermentation of VS3 free cells and immobilized cells showed ethanol production, 19.45+/-0.55 g/L (yield, 0.410+/-0.010 g/g) and 21.66+/-0.62 g/L (yield, 0.434+/-0.021 g/g), respectively. Immobilized VS3 cells showed maximum ethanol production (22.85+/-0.44 g/L, yield, 0.45+/-0.04 g/g) up to 8th cycle during repeated batch fermentation followed by a gradual reduction in subsequent cycles of fermentation.

Ethanol production using Saccharomyces cerevisiae cells immobilised on corn stem ground tissue

Cell immobilisation in alcoholic fermentation has been extensively studied during the past few decades because of its technical and economical advantages over those of free cell systems. A biocatalyst was prepared by immobilising a commercial Saccharomyces cerevisiae strain (baker yeast) on corn stem ground tissue for use in alcoholic fermentation. For this purpose, the yeast cells were submitted to the batch tests 'in situ' adsorption onto pieces of the corn stem ground tissue. Cells immobilisation was analysed by optical microscopy. It was determined that the addition of the corn stem ground tissue led to an increase of the pH value, total dissolved salts content, and sugar content in fermentation medium. The addition of 5 and 10g of the corn stem ground tissue per liter of medium, increased ethanol yield, decreased amount of residual sugar and the cells immobilisation was effective. Corn stem is one of the abundant, available, inexpensive, stable, reusable, nontoxic celulosic biomaterial with high porosity, which facilitates the transmission of substrates and products between carrier and medium. The prepared immobilised biocatalyst showed higher fermentation activity than free cells. The results indicate that corn stem might be an interesting support for yeast cell immobilisation, and also a cheap alternative recourse of mineral components with possibility of application for improving ethanol productivities.