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Very high gravity (VHG) technology was employed on industrial scale to produce ethanol from molasses (fermented) as well as by-products formation estimation. The effect of different Brix° (32, 36 and 40) air-flow rates (0.00, 0.20, 0.40, and 0.60vvm) was studied on ethanol production. The maximum ethanol production was recorded to be 12.2% (v/v) at 40 Brix° with 0.2vvm air-flow rate. At optimum level aeration and 40 Brix° VHG, the residual sugar level was recorded in the range of 12.5–18.5g/L, whereas the viable cell count remained constant up to 50h of fermentation and dry matter production increased with fermentation time. Both water and steam consumption reduced significantly under optimum conditions of Brix° and aeration rate with compromising the ethanol production. Results revealed VHG with continuous air flow is viable technique to reduce the ethanol production cost form molasses at commercial scale.

Soybean molasses, which contains high levels of raffinose family oligosaccharides (RFOs) such as stachyose and raffinose, is subjected to a process of bio-purification to remove sucrose while maintaining the RFOs, consequently increasing its value. This study employed morphological observation, physiological and biochemical studies, and molecular biology techniques to identify YA176, a yeast strain renowned for its effective bio-purification of soy molasses. Through single-factor and orthogonal experiments, optimal bio-purification conditions were established. YA176, belonging to Wickerhamomyces anomalus , demonstrated robust growth across a wide range of temperature and pH levels, coupled with remarkable tolerance to glucose, sucrose, and NaCl up to 41.2%, 47.3%, and 10%, respectively. Under these optimized conditions, YA176 efficiently utilized sucrose while preserving 93.3% of raffinose and 78.6% of stachyose, ensuring the retention of functional RFOs. In summary, yeast strain YA176 exhibits exceptional bio-purification abilities, making it an ideal candidate for producing functional RFOs from soy molasses.

A thermotolerant ethanol fermenting yeast strain is a key requirement for effective ethanol production at high temperature. This work aimed to select a thermotolerant yeast producing a high ethanol concentration from molasses and increasing its ethanol production by mutagenesis. Saccharomyces cerevisiae DMKU 3-S087 was selected from 168 ethanol producing strains because it produced the highest ethanol concentration from molasses at 40 °C. Optimization of molasses broth composition was performed by the response surface method using Box–Behnken design. In molasses broth containing optimal total fermentable sugars (TFS) of 200 g/L and optimal (NH4)2SO4 of 1 g/L, with an initial pH of 5.5 by shaking flask cultivation at 40 °C ethanol, productivity and yield were 58.4 ± 0.24 g/L, 1.39 g/L/h and 0.29 g/g, respectively. Batch fermentation in a 5 L stirred-tank fermenter with 3 L optimized molasses broth adjusted to an initial pH of 5.5 and fermentation controlled at 40 °C and 300 rpm agitation resulted in 72.4 g/L ethanol, 1.21 g/L/h productivity and 0.36 g/g yield at 60 h. Strain DMKU 3-S087 improvement was performed by mutagenesis using ultraviolet radiation and ethyl methane sulfonate (EMS). Six EMS mutants produced higher ethanol (65.2 ± 0.48–73.0 ± 0.54 g/L) in molasses broth containing 200 g/L TFS and 1 g/L (NH4)2SO4 by shake flask fermentation at 37 °C than the wild type (59.8 ± 0.25 g/L). Among these mutants, only mutant S087E100-265 produced higher ethanol (62.5 ± 0.26 g/L) than the wild type (59.5 ± 0.02 g/L) at 40 °C. In addition, mutant S087E100-265 showed better tolerance to high sugar concentration, furfural, hydroxymethylfurfural and acetic acid than the wild type.

Yarrowia lipolytica is a promising platform for single cell oil production. It is well-known for its metabolism oriented toward utilization of hydrophobic substrates and accumulation of storage lipids. Multiple copies of DGA2 under constitutive promoter were introduced into the Q4 strain, a quadruple mutant deleted for the four acyltransferases (Delta dga1, Delta dga2, Delta lro1, and Delta are1) to improve lipid accumulation. The Q4-DGA2 x3 strain contains three copies of DGA2. Further increase in accumulation was accomplished by blocking the beta-oxidation pathway through MFE1 gene deletion yielding Q4-Delta mfe DGA2 x3. In order to use molasses as a substrate for single cell oil production, sucrose utilization was established by expressing the Saccharomyces cerevisiae SUC2 gene yielding Q4-SUC2 DGA2 x3 and Q4-Delta mfe SUC2 DGA2 x3. During cultivation on sucrose medium with a carbon to nitrogen ratio of 80, both strains accumulated more than 40 % of lipids, which was a 2-fold increase in lipid storage. Q4-Delta mfe SUC2 DGA2 x3 accumulated more lipids than Q4-SUC2 DGA2 x3 (49 vs. 43 %) but yielded less biomass (13.7 vs. 15 g/L). When grown on 8 % (v/v) molasses, both strains accumulated more than 30 % of lipids after 3 days, while biomass yield was higher in Q4-SUC2 DGA2 x3 (16.4 vs. 14.4 g/L). Further addition of molasses at 72 h resulted in higher biomass yield, 26.6 g/L for Q4-SUC2 DGA2 x3, without modification of lipid content. This work presents genetically modified strains of Y. lipolytica as suitable tools for direct conversion of industrial molasses into value added products based on single cell oils.

Three culture media were studied for red pigment production by Monascus ruber in submerged cultivation: rice flour (20 g L−1), sugarcane molasses (30 g L−1), and, finally, molasses + rice flour (10 g L−1+10 g L−1); all culture media were added of 5 g L−1 glycine as nitrogen source. Rice flour showed pigment production of 7.05 UA510nm and molasses 5.08 UA510nm, and the mixture of rice flour and molasses showed the best result of 16.38 UA510nm. Molasses culture presented good results for cell biomass production of 11.09 g L−1. With these results, it was observed that one substrate presented good pigment production (rice flour) and another attained better results for cell biomass growth (molasses), and a third medium containing 10 g L−1 of rice flour + 10 g L−1 of molasses was formulated. The results for this mixture showed satisfactory results, with global pigment productivity of 0.097 UA510nm h−1 and maximum productivity rate of 0.17 UA510nm h−1. The high production and productivity obtained for the mixture of rice flour and molasses indicated that the production of red pigment by submerged fermentation, using the mixture of these low-cost culture media, may be promising in terms of commercial production.

2,3-Butanediol has been known as a platform green chemical, and the production cost is the key problem for its large-scale production in which the carbon source occupies a major part. Sugarcane molasses is a by-product of sugar industry and considered as a cheap carbon source for biorefinery. In this paper, the fermentation of 2,3-butanediol with sugarcane molasses was studied by reducing the medium ingredients and operation steps. The fermentation medium was optimized by response surface methodology, and 2,3-butanediol production was explored under the deficiency of sterilization, molasses acidification, and organic nitrogen source. Based on these experiments, the fermentation medium with sugarcane molasses as carbon source was simplified to five ingredients, and the steps of molasses acidification and medium sterilization were reduced; thus, the cost was reduced and the production of 2,3-butanediol was enhanced. Under fed-batch fermentation, 99.5 g/L of 2,3-butanediol and acetoin was obtained at 60 h with a yield of 0.39 g/g sugar.

Molasses wastewater contains high levels of organic compounds, cations, and anions, causing operational problems for anaerobic biological treatment. In this study, an upflow anaerobic filter (UAF) reactor was employed to establish a high organic loading treatment system for molasses wastewater and further investigated the microbial community dynamics in response to this stressful operation. The biogas production increased with an increase in total organic carbon (TOC) loading rate from 1.0 to 14 g/L/day, and then it decreased with further TOC loading rate addition until 16 g/L/day. The UAF reactor achieved a maximum biogas production of 6800 mL/L/day with a TOC removal efficiency of 66.5% at a TOC loading rate of 14 g/L/day. Further microbial analyses revealed that both the bacterial and archaeal communities developed multiple strategies to maintain stable operation of the reactor at high organic loading (e.g., Proteiniphilum and Defluviitoga maintained high abundances throughout the operation; Tissierella temporarily dominated the bacterial community at TOC loading rates of 8.0 to 14 g/L/day; and multi-trophic Methanosarcina shifted as the dominant methanogen at the TOC loading rates of 8.0 to 16 g/L/day). This study presents insights into a high organic loading molasses wastewater treatment system and the microbial flexibility in methane fermentation in response to process disturbances.

The up-flow anaerobic sludge blanket (UASB) reactor is a promising method for the treatment of high-strength industrial wastewaters due to advantage of its high treatment capacity and settleable suspended biomass retention. Molasses wastewater as a sugar-rich waste is one of the most valuable raw material for bioenergy production due to its high organic strength and bioavailability. Interpretation for complex interactions of microbial community structures and operational parameters can help to establish stable biogas production. RNA-based approach for biogas production systems is recommended for analysis of functionally active community members which are significantly underestimated. In this study, methane production and active microbial community were characterized in an UASB reactor using molasses wastewater as feedstock. The UASB reactor achieved a stable process performance at an organic loading rate of 1.7~13.8-g chemical oxygen demand (COD,·L⁻¹ day⁻¹; 87–95 % COD removal efficiencies), and the maximum methane production rate was 4.01 L-CH₄·at 13.8 g-COD L⁻¹ day⁻¹. Lactococcus and Methanosaeta were comprised up to 84 and 80 % of the active bacterial and archaeal communities, respectively. Network analysis of reactor performance and microbial community revealed that Lactococcus and Methanosaeta were network hub nodes and positively correlated each other. In addition, they were positively correlated with methane production and organic loading rate, and they shared the other microbial hub nodes as neighbors. The results indicate that the close association between Lactococcus and Methanosaeta is responsible for the stable production of methane in the UASB reactor using molasses wastewater.

Anaerobic fermentation using lignocellulosic hydrolysates as co-substrates is an economically attractive method to enhance 1,3-propanediol (1,3-PD) production by increasing the conversion yield from glycerol. Lignocellulosic hydrolysates contain the mixed sugars that are primarily glucose, xylose and arabinose. Therefore, these three individual sugars were used, separately, as co-substrates with glycerol, in 1,3-PD production by a Clostridium diolis strain DSM 15410, resulting in an 18%–28% increase in the 1,3-PD yield. Co-fermentation of the mixed sugars and glycerol obtained a higher intracellular NADH/NAD + ratio and increased the 1,3-PD yield by 22% relative to fermentation of glycerol alone. Thereafter, two kinds of lignocellulosic hydrolysates, corn stover hydrolysate and corncob molasses, were individually co-fermented with glycerol. The maximum 1,3-PD yield from glycerol reached 0.85 mol/mol. Fed-batch co-fermentation was also performed, improving the 1,3-PD yield (from 0.62 mol/mol to 0.82 mol/mol). These results demonstrate that the co-fermentation strategy is an efficient and economical way to produce 1,3-PD from glycerol.

Twenty‐six different bacterial strains were isolated from samples taken from different locations Dammam, Saudi Arabia, for screening of their polyhydroxyalkanoate (PHA) production capability. The initial screening was conducted by staining with Sudan Black B and Nile Red, followed by examination under fluorescence and electron microscopes to characterize PHA granule formation. The PHA‐producing bacterial isolates were identified using 16S rRNA gene analyses; the most potent bacterial strain was identified as Pseudomonas sp. strain‐P(16). The PHA production capability of this strain in the presence of different low‐cost carbon sources, such as rice bran, dates, and soy molasses, was analyzed. PHA production in the presence of rice bran, dates, and soy molasses was 90.9%, 82.6%, and 91.6%, respectively. (a) Fluorescence microscopic view exhibiting bright yellowish‐orange color and (b) electron microscopic (EM) view showing PHA granules inside the cells of Pseudomonas sp. strain‐P (16).