Straw Solid-state Fermentation Research Articles

Microbial biomass and phospholipid fatty acid (PLFA) profile changes in bioconversion of wheat straw

Serpula lacrymans was shown to grow rapidly on wheat straw solid state fermentation (SSF). This study aimed to determine the pattern of ergosterol and the relative composition of phospholipid fatty acid (PLFA) produced during fungal growth. The PLFA analysis was carried out on the upper layer of the solvent extraction and was performed on the incubation from 0 up to 35 days. Relative abundant (%) of each fatty acid methyl ester (FAME) produced during the fungal growth was measured by comparing the amount of an individual FAME with the total FAME detected. The dominant PLFA released by the fungi were: 18:2n6c (linoleic acid) 24:1n9 (nervonic acid), 18:1n9c (oleic acid), and 16:0 (palmitic acid). The highest amount of fatty acid produced during the fungal growth is linoleic acid ranged from 186.92-345.78 μg g-1.

Extraction of Vanillin Following Bioconversion of Rice Straw and Its Optimization by Response Surface Methodology

Value-added chemicals, including phenolic compounds, can be generated through lignocellulosic biomass conversion via either biological or chemical pretreatment. Currently vanillin is one of the most valuable of these products that has been shown to be extractable on an industrial scale. This study demonstrates the potential of using rice straw inoculated with Serpula lacrymans, which produced a mixture of high value bio-based compounds including vanillin. Key extraction conditions were identified to be the volume of solvent used and extraction time, which were optimized using response surface methodology (RSM). The vanillin compounds extracted from rice straw solid state fermentation (SSF) was confirmed through LC-ESI MS/MS in selective ion mode. The optimum concentration and yield differed depending on the solvent, which was predicted using 60 mL ethyl acetate for 160 min were 0.408% and 3.957 μg g−1 respectively. In comparison, when ethanol was used, the highest concentration and yields of vanillin were 0.165% and 2.596 μg g−1. These were achieved using 40 mL of solvent, and extraction time increased to 248 min. The results confirm that fungal conversion of rice straw to vanillin could consequently offer a cost-effect alternative to other modes of production.

Biochemical characterization of Serpula lacrymans iron-reductase enzymes in lignocellulose breakdown

Putative iron-reductase (IR) genes from Serpula lacrymans with similarity to the conserved iron-binding domains of cellobiose dehydrogenase (CDH) enzymes have been identified. These genes were cloned and expressed to functionally characterize their activity and role in the decomposition of lignocellulose. The results show that IR1 and IR2 recombinant enzymes have the ability to depolymerize both lignin and cellulose, are capable of the reduction of ferric iron to the ferrous form, and are capable of the degradation of nitrated lignin. Expression of these genes during wheat straw solid-state fermentation was shown to correlate with the release of compounds associated with lignin decomposition. The results suggest that both IR enzymes mediate a non-enzymatic depolymerisation of lignocellulose and highlight the potential of chelator-mediated Fenton systems in the industrial pre-treatment of biomass.

Enhancement of Biogas Production from Bundled Rice Straw Solid-State Fermentation by Adding Microbial Agents

Two contrasting garage-type solid-state fermentation experiments were designed at pilot scale to reveal the intensification process and effects of adding compound inoculants. Bundled rice straw and fresh pig manure were used as feedstock with a total solids concentration (w/w) of 20% under ambient temperatures of 26 to 35 oC. The characteristics of biogas production and variations in bacterial community composition were investigated. The results indicated that using microorganisms shortened the start time of anaerobic solid-state fermentation. The target methane content in the biogas production reached 30% 7 days before the control group. A target of 50% was reached 8 days before the control group. Throughout the fermentation cycle, the cumulative gas production of the experimental group was 1340 m3, which was 20.5% higher than the control group. Cumulative methane production increased by 45%. Clustering and principal coordinates analysis suggested that the addition of compound bacteria increased the diversity of the microbial community and stabilized its structure, thus improving gas production efficiency and methane purity. These findings can assist future bioaugmentation research pertaining to the application of composite microbial agents.

Use of Monascus sp. NP1 for bioethanol production from Cladophora glomerata

The fungus Monascus sp. was able to produce ethanol instead of red pigment under glucose derepression with greater and more tolerance to ethanol than yeast. Algae are known as a polysaccharide resource for bioethanol production. This work was focused on the optimization of cellulase production through solid-state fermentation of straw and rice bran using Trichoderma viride TISTR 3161 for saccharification by the alga, Cladophora glomerata. The best conditions for alga enzymatic hydrolysis were proposed after varying crude enzyme and temperature, comparing the enzyme method to the physical method of saccharification from the alga, characterizing bioethanol production from the fungi at the laboratory scale, and scaling up to a 10-L fermenter, and fermentation of the algal extract at a variety of pH at the laboratory scale. Cellulase production from Sangyod Phatthalung rice using 21.19-mg crude enzyme at 35 °C provided the best conditions of all five varieties of Thai rice tested in terms of producing reducing sugar via algal hydrolysis. This method obtained nearly the same amount of reducing sugar as the physical method (acid and high temperature). At the laboratory scale, 20% glucose in liquid medium was the best condition for ethanol production (1384 μM) of all glucose concentrations tested (2, 10, 20, 30, and 50%) at room temperature on a rotary shaker (110 rpm) for 120 h. The time of production could be reduced to 72 h to produce the same amount of ethanol in a fermenter. The pH of 6 was the proper condition for bioethanol production in algal extract media. The promise of this technique for bioethanol production was shown.

Valorization of Soda Lignin from Wheat Straw Solid-State Fermentation: Production of Oleogels

This work describes the solid-state fermentation (SSF) of wheat straw with Streptomyces sp. MDG147 and further soda-pulping process to obtain wheat straw soda lignins (WSLs). Subsequently, these WSLs were NCO-functionalized with 1,6-hexamethylene diisocyanate and then dispersed in castor oil to achieve stable oleogels. The WSLs were characterized using standard analytical methods, gel permeation chromatography, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Rheological properties of oleogels were determined by means of small-amplitude oscillatory shear and viscous flow measurements. The enzymatic profile and production of lignin–carbohydrate complexes were recorded along the growth time of Streptomyces, whose life cycle was achieved after 7 days. NCO-functionalized WSL was able to chemically interact with castor oil via urethane bonding, providing oleogels with suitable rheological characteristics. Linear viscoelastic functions and viscosity val...

Monitoring the wheat straw fermentation process using an electronic nose with pattern recognition methods

To monitor the wheat straw solid-state fermentation process in real time, an electronic nose (e-nose) was attempted in this study.

Effect of Pb2+ on the production of hydroxyl radical during solid-state fermentation of straw with Phanerochaete chrysosporium

Hydroxyl radical (OH) is a radical species highly destructive for lignin during solid-state fermentation (SSF) of straw with Phanerochaete chrysosporium (Pc). The production of OH at different initial Pb2+ concentrations during SSF of straw with Pc was investigated. The results showed that a modest amount (under 200mgkg−1) of Pb2+ could enhance the production of OH, while a higher Pb2+ concentration resulted in inhibition. The content of OH reached the peak value at day 12 in the whole tested samples, and the maximal content of OH was obtained at initial Pb2+ concentration of 100mgkg−1. It was also found that the production of OH was connected to enzymatic activity and oxalate content in some degree, in particular, a significant positive correlation was found between oxalate concentration and production of OH.We found that low concentration of Pb2+ can promote the degradation of lignin, and the higher initial Pb2+ concentration (400mgkg−1) resulted in inhibition. In addition, it appeared that there was no significant correlation between lignin degradation rate and the production of OH when Pb2+ concentration was taken into account.

Trametes suaveolens as ligninolytic enzyme producer

Species of the genus Trametes represent one of the most efficient lignin-degraders which can be attributed to a well developed ligninolytic enzyme system. Current trends are screening of ability of new species to produce these enzymes, as well as the optimization of conditions for their overproduction. Therefore, the aim of the study was to evaluate the potential of T. suaveolens to synthesize laccase and Mn-oxidizing peroxidases during fermentation of the selected plant raw materials. Level of enzyme activities was measured on 7, 10 and 14th day of submersion, as well as the solid-state fermentation of wheat straw and oak sawdust in the presence of NH4NO3 in previously determined optimal nitrogen concentration of 25 mM. The enzyme activity was determined spectrophotometrically using ABTS and phenol red as the substrates. The highest level of laccase activity (1087.1 U/L) was noted after 7 days of wheat straw solid-state fermentation, while during the submerged cultivation the production of the enzyme was not noted. Submerged cultivation in oak sawdust-enriched medium was the optimal for activity of Mn-dependent peroxidase (1767.7 U/L on day 14) and Mn-independent peroxidase (1113.7 U/L on day 7). Introduction of T. suaveolens to produce ligninolytic enzyme represented the base for further study, as well as the determination of relation between enzyme activity and rate of lignin degradation. It could lead to greater possibility of fungal species selection with high delignification capacity, which could take participation in sustainable production of food, feed, fibres, and energy, environmentally friendly pollution prevention, and bioremediation.

The Research on Solid-State Fermentation Technology of Fuel Ethanol Using in Straw

Based on the introduction of the major problems in solid-state fermentation of straw to produce fuel ethanol and its development direction, this paper systematically discuss the process that currently used.Through analyzing the characteristics of all phases such as pretreatment, hydrolysis and fermentation and so on,we put forward a new kind of process scheme. In this process, we use a mixed method which combined dilute sulfuric acids with steam explosion pretreatment method, after water washing, adopt the method of synchronized saccharification solid-state fermentation,by adding pichia and cellulase enzyme hydrolysis,and we can get ethanol solution at the same time of enzyme hydrolysis. Then through filtered, purified, denatured and so on, at last, we get the fuel ethanol. The equipment that this process requires is simple, and its fermentation have high efficiency high and low energy consumption.

Oxalate production at different initial Pb2+ concentrations and the influence of oxalate during solid-state fermentation of straw with Phanerochaete chrysosporium

The production of oxalate at different initial Pb2+ concentrations during solid-state fermentation of straw with Phanerochaete chrysosporium was investigated. It was found that the maximal peak value of oxalate concentration (22.84mM) was detected at the initial Pb2+ concentration of 200mgkg−1 dry straw, while the minimum (15.89mM) at the concentration of 600mgPb2+kg−1 dry straw, and at moderate concentration of Pb2+ the capability of oxalic acid secretion was enhanced. In addition, it was also found that more oxalic acid accumulation went together with better Pb2+ passivation effect and higher manganese peroxidase (MnP) activity. The present findings will improve the understandings of the interactions of heavy metals with white-rot fungi and the role of oxalate in lignin degradation system, which could provide useful references for more efficient treatment of Pb-contaminated lignocellulosic waste.

Mycelial growth and solid-state fermentation of lignocellulosic waste by white-rot fungus Phanerochaete chrysosporium under lead stress

Lignocellulosic biomass is an abundant renewable resource difficult to degrade. Its bioconversion plays important roles in carbon cycles in nature, which may be influenced by heavy metals in environment. Mycelial growth and the degradation of lignocellulosic waste by lignin-degrading fungus Phanerochaete chrysosporium under lead stress were studied. It was shown that P. chrysosporium could grow in liquid media with 400 mg L −1 Pb(II), and mycelial dry weight was reduced by 54% compared to the control. Yellow mycelia in irregular short-strip shape formed in Pb-containing media, whereas the control showed ivory-white regular mycelial pellets. Two possible responses to Pb stress were: dense hyphae, and secretion from mycelia to resist Pb. During solid-state fermentation of straw, fungal colonization capability under Pb stress was positively correlated with the removal efficiency of soluble–exchangeable Pb when its content was higher than 8.2 mg kg −1 dry mass. Carboxymethyl cellulase activity and cellulose degradation were inhibited at different Pb concentrations, whereas low Pb concentrations increased xylanase and ligninolytic enzyme activities and the hemicellulose and lignin degradation. Cluster analyses indicated that Pb had similar effects on the different microbial indexes related to lignin and hemicellulose degradation. The present findings will advance the understandings of lignocellulose degradation by fungi under Pb pollution, which could provide useful references for developing metal-polluted waste biotreatment technology.

Progress in biopulping of non-woody materials: Chemical, enzymatic and ultrastructural aspects of wheat straw delignification with ligninolytic fungi from the genusPleurotus

During screening of basidiomycetes for wheat straw delignification, considerable lignin degradation with a limited attack to cellulose was attained with Pleurotus eryngii. Straw solid-state fermentation (SSF) was optimized, and the enzymatic mechanisms for lignin degradation were investigated. No lignin peroxidase was detected under liquid or SSF conditions, but high laccase and aryl-alcohol oxidase levels were found. The latter enzyme has been fully characterized in PI. eryngii and it seems to be involved in a cyclic redox system for H202 generation from aromatic compounds. Results obtained using homoveratric acid suggest that Pleurotus laccase could be involved in degradation of phenolic and non-phenolic lignin moieties. Histological and ultrastructural studies provided some general morphological characteristics of the fungal attack on wheat straw. Whereas a simultaneous degradation pattern was observed in straw treated with Phanerochaete chrysosporium, PI. eryngii caused partial degradation of middle lamella and separation of individual sclerenchymatic fibers. When these straw samples were subjected to refining tests, energy saving after biological treatment was the highest in the case of straw treated with PI. eryngii, which also produced the lowest substrate loss. From these results, a correlation between preferential removal of lignin, separation of sclerenchymatic fibers and pulping properties was provided during fungal treatment of wheat straw.

Kinetics of wheat straw solid-state fermentation with Trametes versicolor and Pleurotus ostreatus ? lignin and polysaccharide alteration and production of related enzymatic activities

The kinetics of straw solid-state fermentation (SSF) with Trametes versicolor and Pleurotus ostreatus was investigated to characterize the delignification processes by these white-rot fungi. Two successive phases could be defined during straw transformation, characterized by changes in respiratory activity, changes in lignin and polysaccharide content and composition, increase in in-vitro digestibility, and enzymatic activities produced by the fungi. Lignin composition was analysed after CuO alkaline degradation, and decreases in syringyl/guaiacyl and syringyl/p-hydroxyphenyl ratios and cinnamic acid content were observed during the fungal treatment. An increase in the phenolic acid yield, revealing fungal degradation of side-chains in lignin, was produced by P. ostreatus. The highest xylanase level was produced by P. ostreatus, and exocellulase activity was nearly absent from straw treated with this fungus. Lactase activity was found in straw treated with both fungi, but lignin peroxidase was only detected during the initial phase of straw transformation with T. versicolor. High levels of H2O2-producing aryl-alcohol oxidase occurred throughout the straw SSF with P. ostreatus.

Investigation of physical parameters important for the solid state fermentation of straw by white rot fungi

In laboratory and semi-industrial scale experiments the influence of the substrate water content, temperature, and incubation time on the progress of solid state fermentation of straw colonized by white rot fungi was investigated. The parameters used to evaluate the fermentation process were degradation of total organic matter and lignin, in vitro digestibility, the content of water soluble substances in the substrate and the pH.