Enhancement of butanol production in Clostridium acetobutylicum SE25 through accelerating phase shift by different phases pH regulation from cassava flour

Characterization and potential valorization of industrial food processing wastes

Valorization and utilization of industrial food processing waste as value added products, platform chemicals and biofuels, are needed to improve sustainability and reduce waste management costs. Various industrial food waste stream samples were characterized with respect to their physico-chemical characteristics and elemental composition. A subset of starchy food wastes and milk dust powder were evaluated in batch fermentation to acetone, a useful platform chemical. Production levels were similar to acetone produced from glucose but were achieved more quickly. Lactose concentration negatively affected fermentation and led to 50 % lower acetone concentration from milk dust powder than from starchy wastes. Uncooked starch waste can produce 20 % more acetone than cooked and modified starch waste. Fatty waste and mineral waste can be digested anaerobically generating biogas. Calorific value of soybean waste was 40 MJ/kg sufficiently high for biodiesel production. Low C/N ratios of wastewater and solids from food processing waste makes them unsuitable for anaerobic digestion but these waste types can be converted thermochemically to hydrochar and used as soil amendments. Low calorific content (10-15 MJ/kg) vegetable wastes also are not ideal for energy production, but are rich in flavonoids, antioxidants and pigments which can be extracted as valuable products. A model mapping food waste characteristics to best valorization pathway was developed to guide waste management and future cost and environmental impact analyses. These findings will help advance food industry knowledge and improve sustainable food production through valorized processing waste management.

Integrated Biorefinery and Life Cycle Assessment of Cassava Processing Residue-From Production to Sustainable Evaluation

Commonly known as a subsistence culture, cassava came to be considered a commodity and key to adding value. However, this tuber's processing for starch and flour production is responsible for generating a large amount of waste that causes serious environmental problems. This biomass of varied biochemical composition has excellent potential for producing fuels (biogas, bioethanol, butanol, biohydrogen) and non-energetic products (succinic acid, glucose syrup, lactic acid) via biorefinery. However, there are environmental challenges, leading to uncertainties related to the sustainability of biorefineries. Thus, the provision of information generated in life cycle assessment (LCA) can help reduce bottlenecks found in the productive stages, making production more competitive. Within that, this review concentrates information on the production of value-added products, the environmental impact generated, and the sustainability of biorefineries.

A review on the conversion of cassava wastes into value-added products towards a sustainable environment

The solid and liquid wastes generated from cassava-based industries are organic and acidic in nature, which leads to various global concerns-primarily global warming and biodiversity loss. But the conversion of these wastes into value-added products associated with environmental pollution control contributes to sustainable development. Generally, the thermochemical process such as pyrolysis and gasification and biochemical processes such as anaerobic digestion have been applied for the conversion of cassava waste into value-added products. This review addresses the valorization of cassava wastes, which fulfill almost all needs of the hour, such as energy (biofuel), wastewater treatment (adsorbents), bioplastics, starch nanoparticles, organic acid production, and antimicrobial agents. The major aim of this paper is to analyze and provide the disclosure of the efficiency of cassava-based industrial waste as a source to minimize the problem associated with conventional fossil fuels and through which mitigate the impact of global warming and climate change. Furthermore, recent research and achievements in the valorization of cassava waste have been highlighted.

An Alternative Approach to Improve the Butanol Production Efficiency from Sweet Sorghum Stem Juice Using Immobilized Cells Combined with an In Situ Gas Stripping System

The effects of the nitrogen source and buffers used in butanol production with Clostridium beijerinckii TISTR 1461 from sweet sorghum stem juice (SSJ) containing 60 g/L of total sugar were first studied in this paper. Among the various nitrogen sources (dried spent yeast, urea, ammonium acetate, ammonium sulfate), urea was found to be the most suitable for butanol production. SSJ supplemented with urea (0.64 g/L) and cocktail buffers (KH2PO4, 0.5 g/L; K2HPO4, 0.5 g/L; ammonium acetate, 2.2 g/L) gave the highest butanol concentration (PB, 10.13 g/L). Then, the capability of immobilized C. beijerinckii TISTR 1461 cells for butanol fermentation was investigated. Two residual waste materials were examined as immobilized cell carriers. Bamboo chopstick pieces were more appropriate as carriers for cell immobilization than cigarette filter tips. The PB value of the immobilized cells on the bamboo chopstick pieces was ~13% higher than that on the cigarette filter tips. Using the response surface methodology (RSM), 1.9 cm bamboo chopstick pieces with a carrier loading of 1:32 (w/v) were the optimum conditions for cell immobilization for butanol production. Under these conditions, the PB value was 11.62 g/L. To improve the butanol production efficiency, a gas stripping system (GS) was connected to the fermenter. It was found that the PB (14.02 g/L) and butanol productivity (QB, 0.29 g/L·h) values improved by ~21% compared to butanol fermentation using no gas stripping.

Acetone, butanol, and ethanol production from puerariae slag hydrolysate through ultrasound-assisted dilute acid by Clostridium beijerinckii YBS3

In this study, puerariae slag (PS) was evaluated as a renewable raw material for acetone-butanol-ethanol (ABE) fermentation. To accelerate the hydrolysis of PS, the method of ultrasound-assisted dilute acid hydrolysis (UAAH) was used. With this effort, 0.69 g reducing sugar was obtained from 1 g raw material under the optimal pretreatment condition. Subsequently, the butanol and total solvent production of 8.79 ± 0.16 g/L and 12.32 ± 0.26 g/L were obtained from the non-detoxified diluted hydrolysate, and the yield and productivity of butanol were 0.19 g/g and 0.12 g/L/h, respectively. Additionally, the changes in the structure of PS after different pretreatment methods were observed using SEM and FT-IR. UAAH resulted in more severe and distinct damage to the dense structure of PS. This study suggests that the UAAH is an attainable but effective pretreatment method, thereby is a promising technique for lignocellulose hydrolysis and improve butanol production.

Enhanced butanol-hydrogen coproduction by Clostridium beijerinckii with biochar as cell's carrier

In this study, the effects of biochar on the fermentation performance of butanol-hydrogen coproduction by Clostridium beijerinckii F-6 were investigated. Results showed that the biochar with rich porous and graphitized structure can significantly promote the coproduction of butanol and hydrogen. The productivity of butanol and hydrogen reached 0.148 g/L/h and 0.299 mmol/L/h with biochar addition which were 20.23% and 48.76% higher than that in control without biochar addition, respectively. Moreover, the whole energy conversion efficiency calculated based on the heat value showed increment from 43.69% to 51.75% with biochar addition. Combined analysis of organic acids accumulation and oxidation-reduction potential fluctuation proved that biochar can regulate reducing power during fermentation and accelerate the conversion of acid phase to solvent phase. Scanning electron microscope images showed that biochar acted as carriers for cells absorption. Confirmation experiment further proved that biochar enhanced the butanol tolerant ability of Clostridium beijerinckii F-6.

Effective continuous acetone-butanol-ethanol production with full utilization of cassava by immobilized symbiotic TSH06

BACKGROUND

Butanol production by fermentation has recently attracted increasingly more attention because of its mild reaction conditions and environmentally friendly properties. However, traditional feedstocks, such as corn, are food supplies for human beings and are expensive and not suitable for butanol production at a large scale. In this study, acetone, butanol, and ethanol (ABE) fermentation with non-pretreated cassava using a symbiotic TSH06 was investigated.

RESULTS

In batch fermentation, the butanol concentration of 11.6 g/L was obtained with a productivity of 0.16 g/L/h, which was similar to that obtained from glucose system. A full utilization system of cassava was constructed to improve the fermentation performance, cassava flour was used as the substrate and cassava peel residue was used as the immobilization carrier. ABE fermentation with immobilized cells resulted in total ABE and butanol concentrations of 20 g/L and 13.3 g/L, which were 13.6% and 14.7% higher, respectively, than those of free cells. To further improve the solvent productivity, continuous fermentation was conducted with immobilized cells. In single-stage continuous fermentation, the concentrations of total ABE and butanol reached 9.3 g/L and 6.3 g/L with ABE and butanol productivities of 1.86 g/L/h and 1.26 g/L/h, respectively. In addition, both of the high product concentration and high solvent productivity were achieved in a three-stage continuous fermentation. The ABE productivity and concentration was 1.12 g/L/h and 16.8 g/L, respectively.

CONCLUSIONS

The results indicate that TSH06 could produce solvents from cassava effectively. This study shows that ABE fermentation with cassava as a substrate could be an efficient and economical method of butanol production.

Alkaline pH shock enhanced production of validamycin A in fermentation of Streptomyces hygroscopicus

Validamycin A (Val-A) is produced by Streptomyces as a secondary metabolite with wide agricultural applications of controlling rice sheath blight, false smut and damping-off diseases. The effect of alkaline pH shock on enhancing Val-A production and its mechanism were investigated. A higher yield of Val-A was achieved by NaOH shock once or several times together with faster protein synthesis and sugar consumption and alkaline pH shock can increase Val-A production by 27.43%. Transcription of genes related to amino acid metabolism, carbon metabolism and electron respiratory chain was significantly up-regulated, accompanied by the substantial increase of respiratory activity and glutamate concentration. Val-A production was promoted by a series of complex mechanisms and made a response to pH stress signal, which led to the enhancement of glutamate metabolism and respiration activity. The obtained information will facilitate future studies for antibiotic yield improvement and the deep revealment of molecular mechanism.

Lignocellulosic butanol production from Napier grass using semi-simultaneous saccharification fermentation

Napier grass is a potential feedstock for biofuel production because of its strong adaptability and wide availability. Compositional analysis has been done on Napier grass which was collected from a local area of Taiwan. By comparing acid- and alkali-pretreatment, it was found that the alkali-pretreatment process is favorable for Napier grass. An overall glucose yield of 0.82g/g-glucose_total can be obtained with the combination of alkali-pretreatment (2.5wt% NaOH, 8wt% sample loading, 121°C, and a reaction time of 40min) and enzymatic hydrolysis (40FPU/g-substrate). Semi-simultaneous saccharification fermentation (sSSF) was carried out, where enzymatic hydrolysis and ABE fermentation were operated in the same batch. It was found that after 24-h hydrolysis, followed by 96-h fermentation, the butanol and acetone concentrations reached 9.45 and 4.85g/L, respectively. The butanol yield reached 0.22g/g-sugar_{glucose+xylose}. Finally, the efficiency of butanol production from Napier grass was calculated at 31%.

Enhanced butanol production by solvent tolerance Clostridium acetobutylicum SE25 from cassava flour in a fibrous bed bioreactor

To enhance the butanol productivity and reduce the material cost, acetone, butanol, and ethanol fermentation by Clostridium acetobutylicum SE25 was investigated using batch, repeated-batch and continuous cultures in a fibrous bed bioreactor, where cassava flour was used as the substrate. With periodical nutrient supplementation, stable butanol production was maintained for about 360h in a 6-cycle repeated-batch fermentation with an average butanol productivity of 0.28g/L/h and butanol yield of 0.32g/g-starch. In addition, the highest butanol productivity of 0.63g/L/h and butanol yield of 0.36g/g-starch were achieved when the dilution rate were investigated in continuous production of acetone, butanol, and ethanol using a fibrous bed bioreactor, which were 231.6% and 28.6% higher than those of the free-cell fermentation. On the other hand, this study also successfully comfirmed that the biofilm can provide an effective protection for the microbial cells which are growing in stressful environment.