Simultaneous Saccharification Fermentation Research Articles

Bioconversion of spray corn husks into L-lactic acid with liquid hot water pretreatment

Agricultural by-products like rice husk, bran, and spray corn husks, often utilized as feed, are considered less desirable. This study aims to enhance the utilization rate of these materials by subjecting then to liquid hot water (LHW) pretreatment, followed by enzymatic hydrolysis to produce fermentable sugars. We investigated the production of L-lactic acid using two methods: simultaneous saccharification fermentation (SSF) and separate hydrolysis fermentation (SHF), following varying intensities of LHW pretreatment. The results showed that the optimal enzymatic hydrolysis efficiency was achieved from spray corn husks under the pretreatment conditions of 155 °C and 15 min. SHF was generally more effective than SSF. The glucose L-lactic acid conversion rate in SHF using spray corn husks can reach more than 90 %. Overall, this work proposed a novel, environmental-friendly strategy for efficient and for L- lactic acid production from spray corn husks.

Strategies for the Biotransformation of Tung Leaves in Bioethanol Fermentation

The tung tree (Vernicia fordii Hemsl.), as a woody oilseed crop, has been cultivated in China for thousands of years, and its leaves are rich in cellulose and proteins. The tung leaf is an alternative raw material for the traditional ethanol fermentation of food crops. In this work, the effects of the simultaneous saccharification fermentation of tung leaves at different substrate concentrations on gas production characteristics, reducing sugars, pH, oxidation–reduction potential (ORP), and ethanol yield were investigated during bioethanol production. In addition, the effect of the initial fermentation pH on the ethanol fermentation of tung leaves was explored. The results showed that during bioethanol production from tung leaves, the pH of the fermentation broth showed a continuous decreasing trend. Moreover, the ORP showed a decreasing trend and then rebounded, and the concentration of reducing sugars initially increased and then decreased. The optimal ethanol yield of 4.99 g/L was obtained when the substrate concentration was 100 g/L. Changes in the initial pH have little effect on yeast activity, but such changes can affect the yeast cell wall structure and substance transport, leading to differences in the ethanol yield. When the initial pH is 7, the maximum ethanol yield is 5.22 g/L. The experimental results indicate that the utilization of tung leaves for bioethanol production has a good potential for development.

High-temperature fermentation of corn stover for biodiesel production using Candida tropicalis with enhanced lipid accumulation: A new strategy for breeding thermotolerant biodiesel-production strains

Efficient biodiesel production from biomass is essential for the green-oriented energy transition. The current incongruity between fermentation temperature and microbial thermotolerance is one of the key factors restricting biodiesel production, and it is difficult to solve this problem relying only on conventional microbial characterization and breeding methods. We propose a strategy to solve the corn stover cellulose utilization problem by developing thermotolerant biodiesel-production yeast strains. Candida tropicalis was initially improved by adaptive laboratory evolution and then mutated by atmospheric and room-temperature plasma mutagenesis to obtain a thermotolerant strain capable of growing at temperatures up to 45 °C. Two rounds of fluorescence-activated cell sorting were used to select high lipid content cells, which resulted in a 16.8% increase in lipid accumulation capacity compared to the original cells. The simultaneous saccharification fermentation of the generated strain with pretreated corn stover at 44 °C yielded a lipid generation efficiency of 86.2 ± 2 mg/g. This study provides a new method and an alternative strain for the selection and breeding of high-thermotolerance and high biodiesel-production yeasts and offers a feasible strategy for lignocellulosic fermentation for biodiesel production at elevated temperatures using the new industrial strain.

Bioconversion of cellulose and hemicellulose in corn cob into L-lactic acid and xylo-oligosaccharides

With the banning of antibiotic chemical feed additives, multi-functional bioactive feed additives have been extensively sought after by the feed industry. In this study, low-cost and renewable corn cobs were treated with liquid hot water and converted into bioactive xylo-oligosaccharides and L-lactic acid after enzymatic hydrolysis, strain activation, and fermentation under mild conditions, which achieved a full utilization of cellulose and hemicellulose in corn cobs. Simultaneous saccharification fermentation after strain activation with enzymatic hydrolysate delivered the highest conversion rate of glucose to L-lactic acid (93.00 %) and yielded 17.38 g/L L-lactic acid and 2.68 g/L xylo-oligosaccharides. On this basis, batch-feeding fermentation resulted in a 78.03 % conversion rate of glucose to L-lactic acid, 18.99 g/L L-lactic acid, and 2.84 g/L xylo-oligosaccharides. This work not only provided a green and clean bioconversion strategy to produce multi-functional feed additives but can also boost the full utilization of renewable and cheap biomass resources.

Process simulation of cassava cellulosic ethanol production with low to medium-pressure steam heat integration

Energy demand tends to increase by 80% in 2050 due to the rapid growth of the global population. However, the energy resources rapidly decrease for responding to the global need. Many previous researchers suggest the ideas for solving this situation and the most interesting solution is the heat integration which intends to produce cost-effective energy with minimal impact on the environment. Energy integration thus should be noticeable for the industry process to minimize the loss along the industrial process. The ethanol production process is interested in this study because it can add value to agricultural products like cassava which is an industrial crop in several countries and produces ethanol products that can decrease the usage of gasoline. Here, the heat integration model was developed for the ethanol production process by using low to medium-pressure steam. For the simulation model, the ethanol production process used the cellulose content as the main inlet component to be easy for applicable corresponding to feed casava cellulosic substances. The process contained three sections including enzymatic hydrolysis, simultaneous saccharification fermentation (SSF), and fractional distillation. The quality and quantity of low to medium-pressure steam were investigated for maintaining the operation of the enzymatic hydrolysis reactor by varying steam pressure between 1–2 atm and steam temperature between 100–105 °C. The results achieved the methodology to find optimum conditions by the ratio between steam flow rate and product quantity. The best case could reduce 6.49% of the excessive usage of low to medium-pressure steam which pointed out the way to use the energy efficiently.

Bioconversion of cellulose and hemicellulose in reed sawdust to xylo-oligosaccharides and L-lactic acid

Much of the carbohydrate-rich reed sawdust (RS) produced from the reed pulping mills is burned or buried, causing a waste of resources. The aim of this work is to effectively bio-convert cellulose and hemicellulose of RS to L-lactic acid and xylo-oligosaccharide (XOS) after liquid hot water (LHW) pretreatment. The experiments were carried out via separation hydrolysis fermentation (SHF) and simultaneous saccharification fermentation (SSF) by optimizing the culture and fermentation conditions of a probiotics compound composed of a consortium of lactic acid bacteria. In the end, functional feed additives containing 69.33 wt% L-lactic acid and 26.82 wt% XOS can easily be obtained without additional handling by SSF configuration at 40 ℃ for 82 h with the initial fermentation pH 7.0. The conversion rate of glucose to L-lactic acid reached 72.33%. The bioconversion of available portion in RS into XOS and L-lactic acid paves a new way for high-value utilization of reed residue resources.

Direct production of astaxanthin from food waste by Phaffia rhodozyma

Bioconversion of food waste (FW) into value-added products is a promising approach to solve FW management problem and achieve the global goal of carbon peak and carbon neutralization. In this study, FW could be used as a complete medium to compare the effects of four different fermentation strategies on direct astaxanthin fermentation by Phaffia rhodozyma. The carotenoid production by direct fermentation (DF) reached 129.5 mg/L, increasing by 61.3 %, compared with separate hydrolysis and fermentation (SHF), and carotenoid production by simultaneous saccharification fermentation (SSF) and 1 h pre-hydrolysis SSF (PSSF) were only 20.2 % and 21.5 % higher than DF, respectively. The mechanism of astaxanthin production in the DF could be attributed to the utilization of rice starch due to the production of amylase, and the stimulation of cell growth resulted from the metal elements and the lipid of soybean oil in FW. Remarkably, a 70.3 % increase of carotenoid production was observed when substrate loading increased from 10 % to 20 %. The present study provides a novel process for astaxanthin production from direct bioconversion of FW by P. rhodozyma, which shows potential for low-cost industrial production of astaxanthin.

Pengaruh penambahan surfaktan pada fermentasi tandan kosong kelapa sawit dengan praperlakuan uap air panas bertekanan dengan katalis asam maleat

Oil palm empty fruit bunch (OPEFB) has high potency to be converted into second generation bioethanol production. OPEFB pretreated liquid hot water (LHW) assisted maleic acid (MA) pretreatment was used as substrate in simultaneous saccharification fermentation (SSF). This pretreatment was conducted at 180 °C for 70 min by using 1.5% (w/v) MA acid concentration with material and liquid ratio of 1:14. Subsequently, the pretreated samples were fermented by addition of surfactant, polyethylene glycol (PEG) 4000 and amphiphilic lignin derivatives (A-LD) using Kluyveromyces marxianus InaCC Y119 yeast at temperature of 38 °C for 89 h. Before SSF, pretreated OPEFB was pre hydrolyzed by cellulase enzyme with enzyme loading 30 FPU/g at 50 °C for 3 h. Fermentation filtrate was taken at 0, 24, 48, 72, dan 89 h as much as 1.5 mL for reducing sugar and ethanol content determination. The surfactant addition can enhance reducing sugar and also ethanol content compared to control. The highest ethanol content of 1.251 g/L was found at fermentation of OPEFB pretreated MA with PEG 4000 surfactant at 89 h.

Production of bioethanol and xylitol from non-detoxified corn cob via a two-stage fermentation strategy

A novel two-stage fermentation strategy was applied to produce xylitol and ethanol from the whole acid-pretreated corn cob slurry. The acid-pretreated corn cob was used without filtration and detoxification by the two-stage fermentation with the robust Kluyveromyces marxianus CICC 1727-5. In the first stage, xylose in the slurry after dilute acid pretreatment of lignocellulosic biomass was used to produce xylitol under micro-aeration conditions. In the second stage, simultaneous saccharification fermentation was carried out, and the ethanol was produced from glucose releasing from the solid. Important parameters, such as aeration rate, cellulase loading during xylose utilization and SSF fermentation were studied for best performance. The two-stage fermentation strategy removed the inhibition of glucose on xylose, and little xylose was left in the fermentation broth. Under the optimized condition, the maximum ethanol and xylitol concentration were 52 g/L and 24.2 g/L corresponding to the yield of 0.41 g/g and 0.82 g/g, respectively.

Process simulation of the pilot scale bioethanol production from rice straw by Aspen Hysys

This work is to implement a working model of an integrated process for bioethanol in the process simulation based on rigorous model using the Aspen HYSYS simulation software. As a case study, the simulation is applied to design a pilot plant that converts rice straw into ethanol. The model is based on the process for biochemical conversion of lignocellulosic biomass (rice straw) to ethanol, proposed by the pilot plant of producing bio-ethanol with capacity of 152 kg rice straw/batch. The plant for manufacturing bio-ethanol with rice straw as raw materials comprises basically three units: Pretreatment of rice straw by alkaline treatment; Simultaneous saccharification fermentation (SSF) of rice straw to produce bio-ethanol and the unit for separation and purification of bio-ethanol mixture from simultaneous and fermentation unit. Modeling of rice straw feedstock as a solid material in Aspen HYSYS, including the creation of necessary hypothetical components. Investigate and analyze the final ethanol yield of the simulation project in comparison with actual process. The model proposed was for easily evaluate and analyze various factors which affect to the final ethanol yield by changing operating conditions and being possible to find the optimal conditions for different input flow rate and many independent factors. The simulation model obtained in this study can be applied to any SSF processes with different biomass feedstock.

Caulobacter crescentus β-Xylosidase II Is Highly Tolerant to Inhibitors Present in Fermentative Processes Involving Lignocellulosic Biomass

More stable enzymes with improved properties are in constant demand for various biotechnological processes. In this work, it was found that the activity of recombinant purified β-xylosidase II (CcXynB2) from the bacterium Caulobacter crescentus is increased 62% by 5 mM KCl, likely due to the presence of K+ ions. CcXynB2 activity was measured in the presence of various compounds that have been described as inhibitors of lignocellulosic biomass hydrolysis and fermentation. CcXynB2 was found to be 61% more tolerant than 200 mM ethanol over a 48-h incubation at 37 °C. The specific activity of CcXynB2 was determined in the presence of phenol, hydroxymethylfurfural, ferulic, acetic, and coumaric acids; arabinose, glucose, xylose, and pectin. After 48 h, CcXynB2 activity in the presence of these compounds was found to be equal to 100% or higher than CcXynB2 activity in the absence of these compounds. When inhibitors were used in combination, CcXynB2 retained 67% of its initial activity over 48 h at 37 °C. Enzymatic hydrolysis of hemicellulose from corncobs was performed with CcXynB2 alone or with CcXynB2 in conjunction with recombinant xylanase and β-glucosidase-β-xylosidase-α-arabinosidase from C. crescentus producing reducing sugars. The immobilized CcXynB2 was more active than the soluble enzyme at both temperatures tested, 37 and 50 °C. In addition, immobilized CcXynB2 retained most of the enzyme activity incubated at 50 °C than at 37 °C, maintaining more than 70% of its initial activity after 1 h of incubation. In general, the CCXynB2 has potential to be applied in a bioprocess since it showed robust resistance in presence of many chemical compounds that may be generated during fermentation steps and physicochemical pre-treatment of biomass if considering a simultaneous saccharification fermentation process in a biorefinery.

Improved Cellulosic Ethanol Titres from Highly Lignified Cotton Trash Residues Using Various Batch and Fed-Batch Process Configurations

This study investigates a fed-batch simultaneous saccharification fermentation (F-SSF) process to increase ethanol titres from highly lignified (41.6 wt.%) cotton gin trash residue. The optimal initial solid loading, enzyme dose, feed quantities and intervals to maximize substrate feed and subsequent ethanol titres were examined. Under batch SSF conditions, initial extracted cotton gin trash (ECGT) solid loadings were maximised at 19.35 wt.% and attained an ethanol titre of 23.3 g/l with a corresponding yield of 53.7%. Operating under optimised F-SSF mode, fermentations were initiated with 16.13 wt% EGCT solids followed by fresh ECGT feeds of 16.13 wt% and 12.9 wt.% at 12-h intervals. Cellulase levels were maintained at 44 FPU/g glucan throughout the fermentations. The final ethanol titre of 41 .4 g/l with a corresponding conversion rate of 70.1% was achieved after 72 h. Comparable ethanol yields of 40 g/l with 67.8% conversion were realized with lower cellulase dosing (25 FPU g/glucan) but only after extending the fermentation by 24 h.

Optimization of photo fermentation in corn stalk through phosphate additive

Phosphorus is an essential nutrient for microbial growth which effectively influences the bio‑hydrogen production process. In the present study, the effect of phosphate concentration on simultaneous saccharification fermentation (SSF) hydrogen production by phototrophic microbial consortium has been investigated at various initial pH conditions (6, 7 and 8). The experimental results show that the hydrogen yield has been improved through the addition of phosphate, depending on initial pH and phosphate concentration. The maximum hydrogen yield of 63.09 ± 0.38 mL/g TS and highest energy conversion efficiency of 4.14 ± 0.02% from raw corn stalk were achieved at the phosphate concentration of 4 mmol/L with initial pH value of 6. We have shown that hydrogen yield for raw corn stalk can be enhanced by selecting appropriate amount of the additive. These results may help in optimization of the hydrogen production yield at industrial scale.

Effect of photocatalytic pretreatment of potato starch for bioethanol production using Saccharomyces cerevisiae during simultaneous saccharification-fermentation (SSF)

In this study, the effect of the photocatalytic (PC) pre-treatment with TiO2 during gelatinization (GE) stage in a simultaneous saccharification-fermentation process (SSF) of potato starch for bioethanol production was evaluated. Maximum amount of reducing sugars was 119.3, 114.6 and 104.8 g l-1 for PC→GE, GE→PC and reference (without PC), respectively while bioethanol concentration it increased gradually up to a maximum amount of 128.21, 106.74 and 85.91 g l-1 after 30 h, for PC→GE, GE→PC and reference (without PC), respectively. These results were consistent with the reducing sugars concentration, because bioethanol concentration increased slightly during 18–30 h of fermentation. Although enzymatic activity (ʋmax) for reactions was similar, in reference (without PC pre-treatment) it not promoted quick substrate conversion into ethanol, despite showing the higher affinity enzyme-substrate (Km). Considering traditional potato starch hydrolysis, PC pre-treatment shortened the reaction time of the biological reactions. Thus, the PC pre-treatment of potato starch for bioethanol production could be an environmentally feasible process without acid and alkali addition.

Optimization of sodium percarbonate pretreatment for improving 2,3-butanediol production from corncob

ABSTRACTSodium percarbonate (SP), a kind of alkaline strong oxidant, was applied to corncob pretreatment. The optimized pretreatment conditions were at 4% (w/v) SP concentration with solid-to-liquid (SLR) ratio of 1:10 treating for 4 hr at 60°C. This pretreatment resulted in 91.06% of cellulose and 84.08% of hemicellulose recoveries with 34.09% of lignin removal in corncob. The reducing sugar yield from SP-pretreated corncob was 0.56 g/g after 72 hr of enzymatic hydrolysis, 1.75-folds higher than that from raw corncob. 2,3-butanediol production by Enterobacer cloacae in simultaneous saccharification fermentation was 29.18 g/L using SP-pretreated corncob as a substrate, which was 11.12 times of that using raw corncob. Scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectra analysis indicated that physical characteristics, crystallinity, and structure of corncob had changed obviously after SP pretreatment. This simple and novel pretreatment method was effective for delignification and carbohydrate retention in microbial production of 2,3-butanediol from lignocellulose biomass.

PRODUKSI BIOETANOL SECARA SHF DAN SSF MENGGUNAKAN Aspergillus niger, Trichoderma viride DAN New Aule Instant Dry Yeast PADA MEDIA KULIT UBI KAYU

Effort to improve the yield of bioetanol production from cassava peels were be carried out by separated hydrolysis fermentation (SHF) and simultaneous saccharification fermentation (SSF) using Aspergillus niger, Trichoderma viride and New Aule Instant Dry Yeast. The purpose of this research is to measure bioetanol production from cassava peels using three different culture methods i.e SHF1 (A. niger 24 hours +New Aule Instant Dry Yeast); SHF2 (T. viride 24 hours+New Aule Instant Dry Yeast); and SSF (A. niger + T. viride + New Aule Instant Dry Yeast). The research results showed SHF1 (2,58 g/l) produced higher ethanol than that of SHF2 (2,15). The methods of SSF eficiency produced ethanol (2,93 g/l) and faster (18 hours) compared the methods of SHF1 and SHF2 which need 48 hours incubation time to reach maximum level.
 Keywords: bioethanol, cassava peels, SHF, SSF, A.niger, T.viride, new aule instant dry yeast

High-efficiency bioconversion of kitchen garbage to biobutanol using an enzymatic cocktail procedure

Research on methods to produce biobutanol production from kitchen garbage (KG) as a potential substrate is thus far lacking. Here, the effect of various enzymatic hydrolysis procedures (EHP) was first tested using different enzyme cocktails, on the decomposition of KG. The efficiency of Clostridium acetobutylicum-mediated biobutanol production was then measured using two modes: separate hydrolysis and fermentation (SHF) and simultaneous saccharification fermentation (SSF) in the condition of adjusting pH. The optimal results were obtained using (1) an enzymatic hydrolysis cocktail procedure (EHC5), (2) use of the SSF approach and (3) pH control. This approach results in a biobutanol production of 16.37g/L and total solvent concentration of 32.96g/L. Compared to experiments that use pure glucose asa substrate, our results show that KG is a promising feedstock for biobutanol production. The results demonstrate the feasibility of this waste source for an industrial application via the EHP.

Ethanol production from sweet sorghum bagasse through process optimization using response surface methodology.

In this study, comparative evaluation of acid- and alkali pretreatment of sweet sorghum bagasse (SSB) was carried out for sugar production after enzymatic hydrolysis. Results indicated that enzymatic hydrolysis of alkali-pretreated SSB resulted in higher production of glucose, xylose and arabinose, compared to the other alkali concentrations and also acid-pretreated biomass. Response Surface Methodology (RSM) was, therefore, used to optimize parameters, such as alkali concentration, temperature and time of pretreatment prior to enzymatic hydrolysis to maximize the production of sugars. The independent variables used during RSM included alkali concentration (1.5-4%), pretreatment temperature (125-140°C) and pretreatment time (10-30min) were investigated. Process optimization resulted in glucose and xylose concentration of 57.24 and 10.14g/L, respectively. Subsequently, second stage optimization was conducted using RSM for optimizing parameters for enzymatic hydrolysis, which included substrate concentration (10-15%), incubation time (24-60h), incubation temperature (40-60°C) and Celluclast concentration (10-20IU/g-dwt). Substrate concentration 15%, (w/v) temperature of 60°C, Celluclast concentration of 20IU/g-dwt and incubation time of 58h led to a glucose concentration of 68.58g/l. Finally, simultaneous saccharification fermentation (SSF) as well as separated hydrolysis and fermentation (SHF) was evaluated using Pichia kudriavzevii HOP-1 for production of ethanol. Significant difference in ethanol concentration was not found using either SSF or SHF; however, ethanol productivity was higher in case of SSF, compared to SHF. This study has established a platform for conducting scale-up studies using the optimized process parameters.

Long-term production of bioethanol in repeated-batch fermentation of microalgal biomass using immobilized Saccharomyces cerevisiae

Separate hydrolysis fermentation (SHF) and simultaneous saccharification fermentation (SSF) processes were studied for bioethanol production from microalgal biomass. SSF was selected as an efficient process to enhance the bioethanol yield through repeated-batches using immobilized yeast cells. Combined sonication and enzymatic hydrolysis of Chlamydomonas mexicana generated 10.5 and 8.48g/L of ethanol in SSF and SHF, respectively. Yeast utilized maximum portion of total reducing sugar (TRS) reaching a consumption efficiency of 91–98%. A bioethanol yield of 0.5g/g (88.2% of theoretical yield) and volumetric productivity of 0.22g/L/h was obtained after 48h of SSF. Immobilized yeast cells enabled repetitive production of ethanol for 7 cycles displaying a fermentation efficiency up to 79% for five consecutive cycles. The maximum ethanol production was 9.7g/L in 2nd–4th cycles. A total energy recovery of 85.81% was achieved from microalgal biomass in the form of bioethanol. Repeated-batch SSF demonstrated the possibility of cost-effective bioethanol production.

Enhancing enzymolysis and fermentation efficiency of sugarcane bagasse by synergistic pretreatment of Fenton reaction and sodium hydroxide extraction

A study on the synergistic pretreatment of sugarcane bagasse (SCB) using Fenton reaction and NaOH extraction was conducted. The optimized process conditions for Fenton pretreatment were 10% (w/w) of H2O2, 20mM of Fe2+, pH 2.5, pretreatment time 6h, and pretreatment temperature 55°C. Sequential pretreatments were performed in combination with NaOH extraction (NaOH 1% (w/w), 80°C, 5% of solid loading, 1h). Among all the pretreatments, Fenton pretreatment followed by NaOH extraction had the highest efficiency of 64.7% and 108.3% for enzymolysis and simultaneous saccharification fermentation (SSF) with an ethanol concentration of 17.44g/L. The analyses by the scanning electron microscopy, X-ray diffraction and confocal laser scanning microscopy revealed that Fenton pretreatment disrupts the structure of SCB to facilitate the degradation of lignin by NaOH. The overall data suggest that this combinatorial strategy is a promising process for SCB pretreatment.