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The production of high concentrations of ethanol from N-methylmorpholine N-oxide- (NMMO) and phosphoric acid-pretreated rice straw was investigated at high solid loadings (solid-state) using filamentous fungus Mucor indicus. The impacts of most influential factors on ethanol production by simultaneous saccharification and fermentation (SSF), i.e., enzyme loadings (2.5, 5, 10, and 20 FPU/g substrate), solids loadings (15, 20, and 30% w/w), and SSF time (72 and 120 h), were assessed. The highest glucose concentrations were 106.5 and 94.1 g/L gained from 72-h hydrolysis of the straw pretreated with NMMO and phosphoric acid at 15% (w/w) solids loadings, respectively. The highest ethanol concentrations were 63.4 and 69.0 g/L, achieved by 30% solids loading from 72-h SSF of the straw pretreated with NMMO and phosphoric acid at 20 and 10 FPU celluloses per g substrate, respectively. A prolonged SSF process at enzyme loadings less than 5 FPU/g straw could not improve ethanol concentration from NMMO-pretreated straw, while ethanol concentrations above 40 g/L (61.0 and 59.9 g/L) were achieved through 120-h fermentation of the straw pretreated with phosphoric acid at 30% solid loading. The highest ethanol yields were 73.7 and 100% of the theoretical yield gained from the straw pretreated with phosphoric acid and NMMO, respectively, at the lowest solids loading (15%) and the highest enzyme loading (20 FPU/g substrate).

Organic fraction of municipal solid waste (OFMSW) is dominated by carbohydrates, including starch-based and lignocellulosic materials. The OFMSW was hydrothermally pretreated at 100-160 °C for 0-60 min, and then assessed for enzymatic ethanol production, followed by biogas production from the stillage. The highest glucose yield of 520 g/Kg of dry OFMSW, corresponding to 131% increase compared to that of the untreated OFMSW, was obtained after the pretreatment and enzymatic hydrolysis. Through ethanolic fermentation by an inhibitory tolerant fungus, Mucor indicus, 191.10 g ethanol/Kg of dry OFMSW was obtained, which was a 140.9% improvement in the ethanol yield compared to that from the untreated one. Methane production from the stillage (waste residues) resulted in 156 L/Kg OFMSW. In other words, a total of 10,774 KJ energy/Kg of dry OFMSW was generated at the best conditions.

Kitchen and garden wastes were used for ethanol production and the residue was applied for biogas production. The wastes were pretreated with dilute acid to improve the yield of ethanol production. The pretreatments were carried out with 0.05 M sulfuric acid at 120, 150, and 180 °C for 0, 10, 30, and 60 min, resulting in a liquor mainly containing starchy materials and hemicellulosic sugars and a solid mainly containing cellulose. In order to remove the inhibitors from the liquor, a detoxification step with lime (overliming) was performed. Furthermore, the starch contents of the liquor were enzymatically hydrolyzed before fermentation. Then, the liquor was fermented with ethanolic fungus Mucor indicus, which is a highly inhibitor-tolerant strain of Zygomycetes. After that, the biomasses obtained from aerobic and anaerobic fermentation along with the dilute acid–pretreated solids were subjected to anaerobic digestion for biogas production. The results showed that the addition of fermentation biomass to the pretreated solid significantly improved the biomethane production yield. After pretreatment at 150 °C for 30 min and without detoxification, the maximum amounts of gasoline equivalent of 162.1 and 120.6 L were obtained with and without starch hydrolysis, respectively, where methane production yield was 157.4 mL/g VS and ethanol yields were 75.9% and 94.2%.

In this work, a holistic exergetic-based framework was developed to assess the sustainability and productivity of a batch bioreactor used for ethanol production by ethanolic fungus Mucor indicus . Analyses were carried out in order to identify the most exergetically-sustainable concentration of phosphorous compound to produce ethanol and biomass. The microorganisms were aerobically cultivated using glucose as carbon source at various phosphate concentrations ranging from 0.0 to 7.5 g/L. The results obtained showed that the exergetic parameters of the fermentation process were remarkably influenced by the concentration of phosphate. Generally, the findings achieved revealed 3.5 g/L phosphate concentration as the most optimal fermentation condition from the exergetic point of view. Under this condition, the process exergetic efficiency and normalized exergy destruction as decision making parameters were found to be 53.42% and 0.48 kJ/kJ product, respectively. Moreover, the rational and process sustainability indexes for this concentration were determined at 3.92 and 2.15, respectively. The developed framework could be easily transplanted to evaluate the renewability of various lab-scale biofuel production processes to meet the goals laid forth for sustainable development.

This paper presents an in-depth exergy analysis of the ethanol fermentation process with various forms of fungus Mucor indicus under aerobic and anaerobic conditions to select the most productive and sustainable conditions. Various carbon sources including fructose, glucose, and sucrose as well as the whole and inverted sugar beet and sugarcanes molasses were used during the fermentation. The rational and process exergetic efficiencies were found to be in the range of 65.21%–88.54% and 0.00%–44.31%, respectively. Overall, the exergy-based parameter based on the process outputs could provide useful information about the sustainability and productivity of the fermentation process compared to the rational analysis. More specifically, the inverted sugar beet molasses with MF (mostly filamentous) form of M. indicus under anaerobic cultivation was shown to be the best option for industrial production phase with respect to the productivity and sustainability issues. The results obtained confirmed that the process yield alone cannot perfectly reflect the exact sustainability parameters of the renewable ethanol production systems. Finally, the developed exergetic framework could help engineers to couple biochemical and physical concepts more robustly for achieving the most cost-effective and eco-friendly pathways for bioethanol production.

Recently, Mucor indicus was introduced as a promising ethanol producing microorganism for fermentation of lignocellulosic hydrolysates, showing a number of advantages over Saccharomyces cerevisiae. However, high nutrient requirement is the main drawback of the fungus in efficient ethanol production from lignocelluloses. In this study, application of fungal extract as a potential nutrient source replacing all required nutrients in fermentation of wheat straw by M. indicus was investigated. Wheat straw was pretreated with N-methylmorpholine-N-oxide (NMMO) at 120 °C for 1–5 h prior to enzymatic hydrolysis. Hydrolysis yield was improved at least by 6-fold for 3 h pretreated straw compared with that of untreated one. A fungal extract was produced by autolysis of M. indicus biomass, an unavoidable byproduct of fermentation. Maximum free amino nitrogen (2.04 g/L), phosphorus (1.50 g/L), and total nitrogen (4.47 g/L) as well as potassium, magnesium, and calcium in the fungal extract were obtained by autolysis of the biomass at 50 °C and pH 5.0. The fungal extract as a nutrient-rich supplement substituted yeast extract and all other required minerals in fermentation and enhanced the ethanol yield up to 92.1% of the theoretical yield. Besides, appreciate amounts of chitosan were produced as another valuable product of the autolysis.

Sweet sorghum is one of the most promising energy crops for ethanol production. Fungal solid state fermentation (FSSF) of dry sweet sorghum stalk particles (DSSSPs) for ethanol production was conducted using fungus Mucor indicus and followed by simultaneous saccharification and fermentation of the residual solid without any pretreatment and addition of fresh microorganism cells. The effects of important variables including temperature (28, 32, and 36 °C), moisture level (65, 75, 80, and 85%), initial fungal biomass concentration (0.001, 1, and 5 g/L), and particle size ( 20 mesh) on the yield of ethanol production by FSSF were investigated. The results showed that M. indicus was able to utilize almost all the glucose and fructose within 48 h, whereas the maximum ethanol yield (0.48 g produced ethanol/g consumed sugars) was achieved by FSSF at 32 °C, 80% moisture, and particle size of 20–80 mesh with 5 g/L fungal biomass concentration. Moreover, simultaneous saccharification and fermentation of the stalk glucan (10, 25, and 50 g/L) was performed at 32, 35, and 37 °C with different cellulase and β-glucosidase enzymes loading for 48 h. In the best case, 85.6% of ethanol yield was achieved when 50 g glucan/L was saccharified using 15 FPU cellulase and 30 IU β-glucosidase per gram glucan and simultaneously fermented to ethanol at 37 °C for 48 h. The results indicated that the FSSF acted as a pretreatment stage and assisted the subsequent simultaneous saccharification and fermentation process of the residual solid, resulted in up to 4.3 times improvement in the ethanol production yield.

Biosorption characteristics of Pb +2 ions from aqueous solution were investigated using fungus Mucor indicus biomass treated with NaOH. Biosorption was measured as a function of biomass morphology, pH, biomass concentration, contact time, and metal concentration. The morphology of M. indicus biomass was manipulated towards filamentous or yeast-like forms. The highest and lowest biosorption capacities were observed for purely filamentous and yeast-like forms, respectively. Models of Langmuir, Freundlich, Temkin, and Scachard were applied to describe adsorption isotherm and fitted appropriately. Biosorption kinetics was successfully described using Ho’s pseudo-second-order model. Maximum and minimum values of biosorption capacity of Pb 2+ were 22.1 and 12.1 mg g −1 for purely filamentous and yeast-like morphologies, respectively. Increasing pH resulted in higher biosorption of Pb +2 ions up to pH 5.5. Biosorption capacity of individual Pb +2 ions was reduced in the presence of other metal ions in bi- or multi-metal ion experiments. Metal ions adsorption by the biomass could be eluted effectively with HNO 3 .

The dimorphic fungus Mucor indicus was grown in different forms classified as purely filamentous, mostly filamentous, mostly yeast-like and purely yeast-like, and the relationship between morphology and metabolite production, inhibitor tolerance and the cell wall composition was investigated. Low concentrations of spores in the inoculum with subsequent aeration promoted filamentous growth, whereas higher spore concentrations and anaerobic conditions promoted yeast-like growth. Ethanol was the main metabolite with glycerol next under all conditions tested. The yields of ethanol from glucose were between 0.39 and 0.42 g g(-1) with productivities of 3.2-5.0 g l(-1) h(-1). The ethanol productivity of mostly filamentous cells was increased from 3.9 to 5.0 g l(-1) h(-1) by the presence of oxygen, whereas aeration of purely yeast-like cells showed no such effect. All growth forms were able to tolerate 4.6 g l(-1) furfural and 10 g l(-1) acetic acid and assimilate the sugars, although with different consumption rates. The cell wall content of the fungus measured as alkali insoluble materials (AIM) of the purely yeast-like cells was 26% of the biomass, compared to 8% of the pure filaments. However, the chitosan concentration of the filaments was 29% of the AIM, compared to 6% of the yeast-like cells.

Rice straw was successfully converted to ethanol by separate enzymatic hydrolysis and fermentation by Mucor indicus, Rhizopus oryzae, and Saccharomyces cerevisiae. The hydrolysis temperature and pH ...

The potential of clover (Trifolium repens) and ryegrass (Lolium perenne) mixtures as raw materials for ethanol production was investigated. Wet oxidation, at 175, 185 or 195 degrees C during 10min at two different oxygen pressures and with either addition or no addition of sodium carbonate, was evaluated as pretreatment method for clover-ryegrass mixtures. The enzymatic hydrolysis of cellulose was significantly improved after pretreatment. The highest conversion efficiency, 93.6%, was achieved for the sample pretreated at 195 degrees C, 10min, 1.2MPa and no addition of Na(2)CO(3). For that sample, the overall glucose yield after pretreatment and hydrolysis was 75.5%. No inhibition of cellulose enzymatic conversion by the filtrates was observed. The simultaneous saccharification and fermentation of the pretreated material yielded cellulose conversions of 87.5 and 86.6%, respectively, with Saccharomyces cerevisiae and the filamentous fungus Mucor indicus, and revealed that no addition of nutrients is needed for the fermentation of clover-ryegrass hydrolysates.

The dimorphic filamentous fungus Mucor indicus was used as a biofilter and fermenting microorganism in a bioreactor for continuous cultivation of dilute-acid lignocellulosic hydrolyzates up to dilution rate ( D ) 0.3 h −1 . The hydrolyzate was so toxic that the fungus could not grow in traditional stirred-tank bioreactors even at D 0.1 h −1 . On the other hand, the fungus could be manipulated to grow as a mixture of short dispersed filaments and yeast-like cells. This morphology was suitable to create a biological filter, when attached to a specific screen located across the outlet stream. This filter was fully permeable to the liquid, but not the biomass inside the bioreactor. While the biomass concentration in the outflow was between 0.51 and 3.43 g/l at dilution rates 0.3–0.1 h −1 , the biomass concentration inside the bioreactor was held at 8.34–9.91 g/l. The cells consumed 95.7%, 94.3%, and 75.3% of hexoses and 64.5%, 25.9%, and 7.6% of xylose present in the hydrolyzate at D 0.1, 0.2, and 0.3 h −1 , respectively. The ethanol yields at these dilution rates were 0.37, 0.45, and 0.46 g/g consumed sugars, respectively. The only important by-products were glycerol and xylitol, which at D 0.2 h −1 yielded 0.036 and 0.022 g/g consumed sugars, respectively.

Ethanol production from rice straw by simultaneous saccharification and fermentation (SSF) with Mucor indicus , Rhizopus oryzae , and Saccharomyces cerevisiae was investigated and compared with pure cellulose, Avicel, as a reference. The straw was pretreated with dilute-acid hydrolysis. The SSF experiments were carried out aerobically and anaerobically at 38 °C, 50 g/l dry matter (DM) solid substrate concentration and 15 or 30 filter paper unit (FPU)/g DM of a commercial cellulase. The experiments were ended after 7 days, while an average of 2–3 days were usually enough to achieve the maximum ethanol yield. All the strains were able to produce ethanol from the pretreated rice straw with an overall yield of 40–74% of the maximum theoretical SSF yield, based on the glucan available in the solid substrate. R. oryzae had the best ethanol yield as 74% from rice straw followed by M. indicus with an overall yield of 68% with 15 FPU/g DM of cellulase. Glycerol was the main byproduct of the SSF by M. indicus and S. cerevisiae with yields 117 and 90 mg/g of equivalent glucose in the pretreated straw, respectively, while R. oryzae produced lactic acid as the major byproduct with yield 60 mg/g glucose equivalent in pretreated rice straw under anaerobic conditions.

Ethanol and mycelial biomass production from dilute-acid hydrolyzed hemicellulose fraction of rice straw was investigated by cultivation of Mucor indicus and compared with cultivation of Pichia stipitis. The hydrolysis resulted in 189 g xylose and 29 g glucose per kg of the straw used. Anaerobic cultivation of M. indicus resulted in formation of 0.46 g/g ethanol from glucose, while no ethanol but 0.65 g/g xylitol was produced from xylose. However, the fungus could produce ethanol from both hexoses and xylose present in the hydrolyzate aerobically, and yielded totally 0.24 g/g ethanol and 0.37 g/g mycelial biomass. Xylitol and glycerol were also produced by yields 0.18 and 0.08 g/g, respectively. P. stipitis had a better performance in ethanol production at identical conditions with ethanol yield 0.38 g/g of the sugars within the hydrolyzate.

In searching for ethanol producing microorganisms also capable of fermenting pentoses, nine zygomycetes strains including three strains of Rhizopus oryzae , Mucor corticolous , M. hiemalis , M. indicus , Rhizomucor pusillus , R. miehei , and zygomycete IT were examined. Each strain was cultivated on glucose, xylose or dilute-acid hydrolyzate (DAH) as carbon sources, and the production of ethanol, lactic acid, glycerol, xylitol, and succinic acid were investigated. Great similarities but also conspicuous differences were seen between the species, to some extent linked to the genera. All strains were capable of growing on glucose or xylose as single carbon source. With the exception of the two Rhizomucor strains, all produced ethanol. All the strains produced glycerol as by-product, while Rhizopus and Rhizomucor but not Mucor produced lactic acid in significant amounts. All Mucor and Rhizopus strains and one strain of Rhizomucor produced xylitol in the xylose medium, but no xylitol was detected after growth on DAH. All Mucor and two R. oryzae strains were capable of growing on DAH. Two Mucor species, M. hiemalis and M. indicus showed greater ethanol production than the other strains. The ethanol yields by M. hiemalis on glucose, xylose, and DAH were 0.39, 0.18, and 0.44 g/g, respectively, whereas the corresponding results for M. indicus were 0.39, 0.22, and 0.44 g/g. The strains also rapidly consumed hydroxymethyl furfural present in DAH.

Chitosan is obtained by chemical conversion of chitin, which is a constituent of the exoskeleton of crustacea and insects. An alternative source of chitosan is the cell wall of fungi. Fungal culture media and fermentation condition can be manipulated to provide chitosan of more consistent physico-chemical properties compared to that derived chemically from chitin. Chitosan has been isolated from Mucor rouxii cultured in three different media, viz., molasses salt medium (MSM), potato dextrose broth (PDB) and yeast extract peptone glucose (YPG) medium under submerged condition and their yield has been found to be the almost same, being 0.61 g/l for MSM, 0.51 g/l for PDB and 0.56 g/l for YPG respectively. Their physico-chemical properties such as ash, moisture, protein contents and specific rotation do not show much difference. However, variation has been observed in their polydispersed nature and crystallinity. Chitosan from MSM was less polydispersed and more crystalline compared to those from YPG and PDB.

A survey of the microbiological quality of commercial tempeh was done in The Netherlands. A total of 110 samples were examined. Most (98%) of the samples had an aerobic plate count above 107 CFU/g. Numbers of Enterobacteriaceae exceeded 105 CFU/g in 67% of the samples, whereas numbers of lactic acid bacteria exceeded 107 CFU/g in 81% of the samples. Staphylococcus aureus was found in 13%, Bacillus cereus in 11% and Escherichia coli in 3% of the samples at levels of 105 CFU/g. Yersinia enterocolitica was found in six samples, whereas Salmonella was absent in 25 g of all the samples examined. Many (69%) of the samples had a yeast count above 105 CFU/g. Trichosporon beigelii was the most frequent yeast species. Besides Rhizopus oryzae and Rizopus oligosporus , which obviously represent the mold species responsible for the fermentation, Mucor indicus was often associated with the mycoflora of the tempeh. The reasons for the poor microbiological quality are discussed and some recommendations are proposed.