Use of post-harvest sugarcane residue for ethanol production

Agricultural residues are produced in large quantities throughout the world. Approximately, 1kg of residue is produced for each kilogram of grains harvested. This ratio of grain/residue translates into an excess of 40 billion ton of crop residue produced each year in the USA. These residues are renewable resources that could be used to produce ethanol and many other value added products. In this study, we demonstrate that the post-harvest sugar cane residue could be used to produce fuel grade ethanol. A chemical pre-treatment process using alkaline peroxide or acid hydrolysis was applied to remove lignin, which acts as physical barrier to cellulolytic enzymes. Yeast Saccharomyces cerevisiae ATCC strain 765 was used in the experiment. The pre-treatment process effectively removed lignin. Ethanol production in the culture sample was monitored using high performance liquid chromatography. The results indicate that ethanol can be made from the sugarcane residue. The fermentation system needs to be optimized further to scale up the process for large-scale production of ethanol from sugar cane residue.     

Simulation of sugarcane residue decomposition and aboveground growth

Due to the worldwide increase in demand for biofuels, the area cultivated with sugarcane is expected to increase. For environmental and economic reasons, an increasing proportion of the areas are being harvested without burning, leaving the residues on the soil surface. This periodical input of residues affects soil physical, chemical and biological properties, as well as plant growth and nutrition. Modeling can be a useful tool in the study of the complex interactions between the climate, residue quality, and the biological factors controlling plant growth and residue decomposition. The approach taken in this work was to parameterize the CENTURY model for the sugarcane crop, to simulate the temporal dynamics of aboveground phytomass and litter decomposition, and to validate the model through field experiment data. When studying aboveground growth, burned and unburned harvest systems were compared, as well as the effect of mineral fertilizer and organic residue applications. The simulations were performed with data from experiments with different durations, from 12 months to 60 years, in Goiana, Timbaúba and Pradópolis, Brazil; Harwood, Mackay and Tully, Australia; and Mount Edgecombe, South Africa. The differentiation of two pools in the litter, with different decomposition rates, was found to be a relevant factor in the simulations made. Originally, the model had a basically unlimited layer of mulch directly available for decomposition, 5,000 g?m^?2. Through a parameter optimization process, the thickness of the mulch layer closer to the soil, more vulnerable to decomposition, was set as 110 g?m^?2. By changing the layer of mulch at any given time available for decomposition, the sugarcane residues decomposition simulations where close to measured values (R ² ?=?0.93), contributing to making the CENTURY model a tool for the study of sugarcane litter decomposition patterns. The CENTURY model accurately simulated aboveground carbon stalk values (R ² ?=?0.76), considering burned and unburned harvest systems, plots with and without nitrogen fertilizer and organic amendment applications, in different climates and soil conditions.     

White-rot fungal growth on sugarcane lignocellulosic residue

Summary Twelve white-rot fungi were grown in solid state culture on sugarcane chips previously fermented by yeast employing the EX-FERM process. The lignocellulosic sugarcane residue had 12.5% permanganate lignin and 81.3% holocellulose. After 5 to 6 weeks at 20° C, all fungi produced a solid residue which had a lower in vitro dry matter enzymatic digestibility than the original bagasse, with the exception of Coriolus versicolor which showed a slight increase of 0.6 units. Four fungi produced a residue with higher soluble solids than the original sample. Lignin losses were rather similar for all fungi tested, an average value of 38.64% of the original value was obtained. About the same amount of hemicellulose was degreaded, 32.22%. Most fungi showed a preference for hemicellulose hydrolysis over cellulose degradation. The two fungi that showed greater cellulolytic activity were Sporotrichum pulverulentum and Dichomitus squalens. No appreciable dry matter losses were detected for Agrocybe aergerita and Flammulina velutipes.     

Microbial communities in sugarcane field soils with and without a sugarcane cropping history

Microbial communities in rhizosphere soil from sugarcane (Saccharum inter-specific hybrids) and bulk soil were compared at paired field sites with and without a sugarcane cropping history to determine whether monoculture affects soil microbial community composition. Differences were evaluated for culturable microorganisms and functional diversity indicated by community level physiological profiles (CLPP). Qualitative differences in rhizosphere bacterial communities were detected between sites with no sugarcane cropping history (N_site) and sites with a long-term sugarcane cropping history (L_site). More fluorescent pseudomonads were detected in N_site than L_site rhizosphere soil at two of three sites, and Actinobacteria were more numerous in N_site than L_site rhizosphere soil at one site. Fusarial fungi were more numerous in N_site than L_site rhizosphere soils. Bacteria were more numerous in rhizosphere soil compared to bulk soil. Total bacterial, pseudomonad, and Actinobacteria population densities were greater in bulk soil from an N_site compared to an L_site. CLPP distinguished bulk from rhizosphere soil at one of two sites and N_site and L_site rhizosphere soils at two of four sites. Site affected CLPP similarity more than cropping history. The results demonstrated that sugarcane monoculture can affect the composition of the microbial community in field soil. The findings have possible implications for reduced yields associated with sugarcane monoculture.     

Microbial decomposition of coumarin in soil

Microbial decomposition of coumarin was studied in samples of chernozem soil by manometric measurement of oxygen consumption, paper chromatography of aromatic metabolic intermediates in soil extract and measurement of their UV spectra, and by the technique of simultaneous adaptation. Coumarin is decomposed in soil viao-coumaric and melilotic acids and at least one other compound of aromatic character. The metabolic pathway including salicylic acid and catechol was not proved. A total of 39 strains of coumarin-decomposing bacteria were isolated from the soil, out of which 25 belong to the genusPseudomonas, 7 to the genusCellulomonas and 7 to the genusAchromobacter. A comparison of the counts of bacteria utilizing coumarin as a sole carbon source in garden soil, in two chernozem soil samples and in acidic brown soil showed that their occurrence bears no relation to the so-called total number of bacteria (grown on agar medium with yeast and soil extracts and with tryptone) or to the content of carbon and nitrogen in the soil, or to its acidity.     

Microbial changes during oil decomposition in soil

An examination has been made of the changes in bacterial and fungal populations during the decomposition of oil in contaminated soil. The number of aerobic and anaerobic bacteria and the length of mycelium increased in the oily soil whereas the number of CFU (= colony forming units) of fungi was highest in a control soil. The percentage of oil-utilizing fungi increased from 60% to 82%, while the bacterial utilization figure increased from 3% to 50%. The important oil-utilizing fungus Scolecobasidium appeared only in the oily soil, but otherwise the composition of the fungal flora changed only little after addition of oil. In laboratory experiments the chemical Pajab FI was shown to increase microbial activity.     

Microbial decomposition of urea in the Menai Straits

The assimilation of urea by the microbial population of the Menai Strait (Anglesey, U.K.) was studied over a seasonal cycle. Samples incubated in the light produced higher assimilation rates than samples incubated in darkness. Higher ratios assimilation of urea: chlorophyll a during a time of a probable nitrogen limiting condition may be indicative of the importance of urea for phytoplankton nutrition. Assimilation rates of urea were higher during the diatom and Phaeocystis bloom than in times of low standing crop.Phytoplankton seem to be the major utilizers of urea in the Menai Strait waters. Bacteria may also be important in the decomposition of urea. However, with the methods employed it was not possible to estimate the extent of their participation in the urea decomposition.     

Microbial decomposition of leaf litter as influenced by fertilizers

Summary A urea and NPK-mixture at concentration of 5, 10 and 15 mg g^–1 air dry litter stimulated microbial populations, microbial activity and rate of decomposition of the litter. The stimulation was more pronounced as the concentration of the fertilizers was increased. However, this trend was reverse after two months in case of urea except for bacterial population. Fewer fungal species were isolated from the fertilizer-treated litter, together with a certain degree of alteration in the composition of mycoflora.     

Microbial decomposition of carboxymethyl cellulose continuously added to the soil

If heterocontinuous flow-cultivation method was used to study the degradation of soluble carboxymethyl cellulose (CMC) in soil, neither the potential CM-cellulase activity of the soil nor the total degree of CMC mineralization significantly differed under aerobic condition and in a nitrogen atmosphere. In contrast, the end products of the enzymatic hydrolysis and their mutual proportions were different: under anaerobic conditions, the formation of reducing sugars was increased at the expense of CO₂ production and organic acids were detectable in the extract. The composition of soil microflora also differed. Addition of ammonium ions affected the maximum CM-cellulase activity in the soil, the degree of substrate mineralization, the proportion of CO₂ and reducing sugars that are formed and the concentration of the present soil microflora.     

Microbial decomposition of dissolved organic matter in a hypertrophic pond

Planktonic heterotrophic bacteria in lakes utilize the labile fraction of dissolved organic carbon (DOC), although information about seasonal changes in labile DOC in hypertrophic lakes in terms of absolute amount and relative proportion of the total DOC is still limited. We conducted DOC decomposition experiments using GF/F filtrates in water samples from hypertrophic Furuike Pond, together with monitoring of DOC concentration and bacterial abundance in water samples from the pond, to examine seasonal changes in the amount of labile DOC and growth of bacteria on labile DOC. DOC concentrations fluctuated between 2.7 and 11 mg C l⁻¹, and bacterial abundance fluctuated between 1.5 × 10⁶ and 1.0 × 10⁸ cells ml⁻¹. In the DOC decomposition experiment when grazers of bacteria were removed, small portions of DOC (18% ± 12%) were labile for decomposition by bacteria, and the growth yield of bacteria on labile DOC ranged between 3.3% and 19%. Furthermore, addition of nitrogen to water samples enhanced bacterial growth. Thus, not only labile DOC but also nitrogen limited bacterial growth in the pond. Considering the results in the present study together with those of previous studies, bacterial abundance in Furuike Pond is subjected to bottom-up control, such as by limitation of DOC and nitrogen throughout the year, although top-down control of bacterial abundance such as by grazing is seasonally important. Received: May 1, 2001 / Accepted: July 22, 2001     

An effective surfactant-assisted hydrothermal pretreatment strategy for bioethanol production from chili post-harvest residue by separate hydrolysis and fermentation

Bioprocess and Biosystems Engineering - Surfactants play major role in the delignification of lignocellulosic biomass. Surfactant-assisted hydrothermal pretreatment was evaluated for chili...     

Elevated CO2 alters the rhizosphere effect on crop residue decomposition

Plant and Soil - This study tested the capacity of the semi-aquatic grass Echinochloa stagnina to grow on highly salt-affected soil to improve soil structure and decrease salinity of saline...     

Microbial decomposition of freshwater macrophytes in the littoral zone of lakes

The decomposition of several lake macrophytes was investigated under field conditions. Data on weight and phosphorus loss, numbers of microbial decomposers and their activity were obtained.Experiments were conducted in the littoral of two lakes with different levels of macrophyte development.Weight loss during 40–60 days of decomposition for fast-decomposing plants was 60–95% and after 365-day of incubation, Potamogeton perfoliatus L. lost nearly 100% of its initial weight. Slow-decomposing plants lost 20–50% of their initial weight after 40–60 days of incubation, and Phragmites australis (Cav.) Trin. ex Steud. lost 84% of its initial weight after 365 days.Total phosphorus content in plants did not decrease at the first stages of decomposition.The number of microbial decomposers utilizing both labile and resistant substrates increased 2–6 times during the first 5–25 days period. During this period the community was morphologically diverse and biochemically active (high level of microbial respiration). It coincided with the highest weight loss. After that period, the number of microorganisms utilizing labile substrates, as well as the rate of decomposition decreased.The part of macrophyte organic matter entering the biological cycle in two lakes made up 3.5% and 26% of phytoplankton primary production. Bacterial production on decomposing macrophytes was calculated at 4% and 51% of bacterioplankton production, respectively, in both lakes.     

Microbial decomposition of 3,4-dichloroaniline, adsorbed by activated charcoal]

The accessibility of 3,4-dichloroaniline (DCA) sorbed by activated carbon to degradative microorganisms was studied. A Paracoccus denitrificans strain capable of growing on medium with DCA as the only source of energy, carbon, and nitrogen was used in the experiment. The high sorption capacity of all the carbons studied (powdered RS and SKT-6A and granular AG-3) in relation to DCA (350 to 360, 480 to 520, and 540 to 580 mg/g, respectively) was demonstrated. The sorption capacity correlated positively with the specific surface area and the total volume of the sorbent micropores. The bulk of the DCA was reversibly sorbed and amenable to microbial decomposition; however, the decomposition rates significantly differed. When RS, SKT, and Agrosorb preliminarily saturated with DCA were incubated in a culture of P. denitrificans, the bulk of the reversibly sorbed DCA was decomposed (in the absence of the other carbon sources) in 2, 5, and 10 weeks, respectively, after which the process slowed down. At the end of the experiment (29 weeks), 81 to 87% of the DCA underwent full mineralization, which was accompanied by the release of chlorine ions; a small fraction of the xenobiotic (0.8 to 1.9%) remained a reversibly sorbed fraction (extractable with acetone), and 12 to 17% of the initial DCA seemed to have been chemically transformed and bound by carbon. The studied carbons may be used in biological decontamination of chloroaniline-polluted soils to decrease the toxic effect of chloroanilines on microorganisms.     

Microbial activity during leaf decomposition in an Alaskan subarctic stream

Fungal biomass and growth and microbial respiration were studied for two field seasons in a second-order subarctic stream where water temperature is 0°C for approximately 6 months. Leaf packs (5-g) of alder Alnus tenuifolia , birch Betula papyrifera and willows Salix alaxensis and Salix arbusculoides immersed in autumn of 1979 and 1980 were sampled until June 1980 and January 1981, respectively. Fungal growth and microbial respiration occurred in submerged detritus at 0°C. Total and FDA-active hyphal lengths were measured, the active proportion averaging 25% of the total (all leaf species, both years). Generally, microbial respiration peaked in all leaf species after two weeks in the stream. As water approached 0°C, respiration declined by 20–50% depending on leaf species, but often increased later in decomposition (at 0°C). Seasonal trends in microbial respiration and FDA-active hyphal lengths were not similar although maximal respiration usually occurred as FDA-active hyphae were growing most rapidly. The calculated leaf weight loss due to microbial respiration was small (7–10%) in all leaf species, compared with total weight loss over 98 d. Scanning electron microscopy provided a visual record of leaf surface microorganisms and apparent leaf cuticle dissolution by fungi and bacteria.