Browsing by Author "Pihlajaniemi, Ville"

Now showing 1 - 16 of 16

Ammonia recycling after soaking ensiled grass in aqueous ammonia for improved hydrolysability
(2017-10-03) Poikkimäki, Sakari
Kemian tekniikan korkeakoulu | Master's thesis
Ensiled grass is a potential low-cost biorefinery feedstock with surplus production capacity in Europe and properties suitable for advanced animal feed applications and biochemical production. In a typical biorefinery concept, pretreatment of lignocellulosic biomass is required for facilitating enzymatic hydrolysis of carbohydrates in biorefineries. However, due to its cost intensive nature, pretreatment is one of the main reasons why lignocellulose has not yet been utilised fully. Soaking in aqueous ammonia (SAA) is a promising pretreatment process that is being improved for more cost-effective lignocellulose saccharification. Still, the recovery and recycling of ammonia in this process has not been thoroughly researched on to improve the feasibility of the process. The current thesis aimed to study the recovery of ammonia from ammonia pretreated grass silage with simple distillation methods and to determine the effects the recovery has on the yield of enzymatic hydrolysis. A larger scale single-reactor process for ammonia soaking, recovery and enzymatic hydrolysis was demonstrated. Three different ammonia loading ratios in SAA were used to find out the effects on the hydrolysis and ammonia yield in the recovery process. The recovery of ammonia was successful and the best results were gained in the single-reactor study where 66 % of the ammonia was recovered by only evaporating 12 % of the total liquid. The ammonia was recovered as an aqueous solution at a concentration sufficiently high for efficient recycling. The recovery process did not have any detrimental effects on the enzymatic hydrolysis and 10 % ammonia loading was sufficient for efficient pretreatment, leading to hydrolysis yields up to 86 %. The study carried out in this thesis concluded that the recovery of ammonia from SAA can be efficiently performed with simple equipment under atmospheric pressure. Especially the single-reactor process combined with simple recycling method could potentially be utilised in local and decentralised processing of ensiled grass.
Autohydrolysis and aqueous ammonia extraction of wheat straw: effect of treatment severity on yield and structure of hemicellulose and lignin
(2014) Sipponen, Mika; Pihlajaniemi, Ville; Sipponen, Satu; Pastinen, Ossi; Laakso, Simo
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The objective of this study was to elucidate the impact of autohydrolysis severity on the yield and structure of wheat straw hemicellulose and lignin. The autohydrolysis treatments were carried out at maximum temperatures between 170 °C and 200 °C. The autohydrolysis liquors were separated and the solids were successively extracted with aqueous ammonia either in moderate or high intensity extraction conditions to dissolve lignin for analysis. Increasing autohydrolysis severity decreased the molar mass of the aqueous ammonia extracts from 5450 g mol−1 to 1810 g mol−1, and carbohydrate content from 6% to 0.1%. The optimum autohydrolysis severity (log R0 = 3.81) for xylan recovery released mainly oligomeric arabinoxylans at 66% xylan recovery yield. Drastic degradation of pentoses occurred beyond the optimum severity. As an indication of accumulation of “pseudo-lignin” during autohydrolysis, decreasing relative aromaticity in the aqueous ammonia extracts as a function of autohydrolysis severity was shown. The finding was confirmed by quantitative analysis of the cupric oxide oxidation products of lignin suggesting up to 55% decrease in the relative amount of native lignin at the highest severity. These results show the importance of distinguishing between lignin and “pseudo-lignin” in fractions obtained from lignocellulosic materials subjected to acidic pretreatment.
Calcium Chelation of Lignin from Pulping Spent Liquor for Water-Resistant Slow-Release Urea Fertilizer Systems
(2017-01) Sipponen, Mika Henrikki; Rojas, Orlando J.; Pihlajaniemi, Ville; Lintinen, Kalle; Österberg, Monika
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Slow-release fertilizers represent a possible large-scale application for plant polymers. Here we show a facile way to stabilize urea in fertilizer systems by lignin. Chelation of kraft black liquor with calcium acetate at pH 13 precipitated lignin as a calcium complex (Ca-lignin), which offered beneficial effects if compared to those from lignin obtained by precipitation at low pH (Acid-lignin). The reduced affinity of water to Ca-lignin was exploited in the formulation of slow release fertilizers comprising wheat straw sections impregnated with Ca-lignin in molten urea. Compared to the case of Acid-lignin, immersion in water was slowed down more extensively by Ca-lignin. After 24 h incubation at low moisture conditions, the highest proportion of urea retained in the Ca-lignin/straw fertilizer system was 58%. The water resistance of Ca-lignin was explained by a lower aqueous solubility that differed from the typical pH-dependent solubility of Acid-lignin. Electron microscopy, infrared spectroscopy, and accessible surface areas suggested that Ca-lignin consisted of less densely packed molecules organized as calcium-chelated chains. Overall, the controlled water-solubility of lignin precipitated by metal cations is greatly beneficial in fertilizer systems and can open new opportunities in material development (permeable films and others).
Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption
(2014) Sipponen, Mika Henrikki; Pihlajaniemi, Ville; Littunen, Kuisma; Pastinen, Ossi; Laakso, Simo
School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m2/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available.
The effect of soluble phenolic compounds from hydrothermally pretreated wheat straw on Trichoderma reesei cellulases and commercial enzyme cocktails
(2024-01) Borisova, Anna S.; Pihlajaniemi, Ville; Kont, Riin; Niemelä, Klaus; Koitto, Taru; Mikkelson, Atte; Väljamäe, Priit; Kruus, Kristiina; Marjamaa, Kaisa
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Hydrothermal methods are commonly applied in pretreatment of lignocellulose for conversion to biofuels and chemicals. This pretreatment partially disassembles and solubilizes hemicelluloses and lignin, releasing sugars and phenolic compounds, which are potential inhibitors for the subsequent enzymatic saccharification step. In this work, the inhibitory effect of soluble phenolics in hydrothermal pretreatment liquor on canonical Trichoderma reesei enzymes was investigated, using purified cellobiohydrolases, endoglucanases, a xylanase, and a lytic polysaccharide monooxygenase, as well as commercial enzyme cocktails Cellic Ctec2 and Celluclast. The pretreatment liquor was fractionated to enrich the phenolics, and thoroughly analyzed. The most sensitive to phenolics inhibition were cellobiohydrolases, the major enzymes in crystalline cellulose degradation and the primary component in cellulolytic mixtures. These were inhibited by the oligophenolics and phenol-carbohydrate complexes (lignin-carbohydrate complex type of compounds), the latter of which could be mitigated by other enzymes, i.e., xylanases and endoglucanases. Addition of lytic polysaccharide monooxygenase to the hydrolysis reactions was found to relieve the negative effect of phenolics. Similarly, hydrolytic activity of a commercial enzyme cocktail Cellic Ctec2 was enhanced in the presence of low concentrations of phenolics.
Fractionation process for the protective isolation of ergosterol and trehalose from microbial biomass
(2017-07) Pastinen, Ossi; Nyyssölä, Antti; Pihlajaniemi, Ville; Sipponen, Mika Henrikki
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
A new process is described for the two phase extraction of ergosterol and trehalose from microbial biomass. Baker's yeast was used as a model organism to develop the method, which was then applied for extracting 13 oleaginous microbes. Major findings of the study were that the ergosterol content was not dependent on intracellular oil content and that 1-butanol and alkaline pH were needed to protect ergosterol. Saponification for 3-4. h at 85-100. °C followed by extraction of the reaction mixture with toluene gave the maximal ergosterol yield. Trehalose was stable at this temperature and remained in water solution, but the maximal yield was obtained after a shorter reaction time at lower alkalinity. Although trehalose alone is stable at alkaline pH, extraction yields of trehalose from yeast decreased with increasing alkalinity. This finding led us to propose a two-step process in which trehalose is separated in the first step and ergosterol in the second. The possibility to apply this method to fractionate oleaginous microbes in process scale is discussed from technical viewpoints.
Integrating the opposites of biofuel production: Absorption of short-chain alcohols into oleaginous yeast cells for butanol recovery and wet-extraction of microbial oil
(2016) Sipponen, Mika Henrikki; Pihlajaniemi, Ville; Vainio, Heidi; Essi, Palonen; Hokkanen, Sanna; Vahvaselkä, Marjatta; Pastinen, Ossi; Nyyssölä, Antti; Laakso, Simo
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Recovery of two biotechnologically produced fuel components, butanol and microbial oil, is assessed by absorption of the six shortest 1-alcohols into oleaginous yeast cells. We show an unexpectedly high extent of absorption of >C3 alcohols from water into Rhodosporidium fluviale cells with a lipid content of 69% of cell dry weight (CDW). Increasing the carbon chain length of the alcohol boosts both the rate and the quantity of absorption of the alcohol from water containing an initial ratio of 9.5 of CDW to alcohol. Under these conditions, 40% of butanol is removed from water, while the methanol concentration remains unchanged in 48 h incubation with the oleaginous yeast cells. Lower absorption of alcohols into non-oleaginous baker's yeast cells as a reference suggests that a majority of the alcohols combines with the lipid droplets inside oleaginous cells. The partition coefficient of the intracellular microbial oil to butanol exceeds those of oleyl alcohol and rapeseed oil by factors of 4 and 16. The capacity of oleaginous yeast cells to absorb butanol reaches 13% of CDW from 48 g per L butanol solution. Leakage of intracellular microbial oil occurs when the initial butanol concentration exceeds approximately 20 g L-1. Butanol can be recovered after absorption from oleaginous yeast biomass, while microbial oil can be separated by subsequent wet-extraction with the alcohols as solvents. These results suggest that synergistic outcomes can be achieved by process integration both for industry and the environment.
Lignoselluloosamateriaalien mikroskooppiset kuvantamismenetelmät
(2012) Hämäläinen, Joonas
Kemian tekniikan korkeakoulu | Bachelor's thesis
Modeling and optimization of polyethylene glycol (PEG) addition for cost-efficient enzymatic hydrolysis of lignocellulose
(2021-03) Pihlajaniemi, Ville; Kallioinen, Anne; Sipponen, Mika; Nyyssölä, Antti
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Enzyme consumption is a key cost in the lignocellulosic sugar route for production of biofuels and chemicals, and polyethylene glycol (PEG) is a low-cost additive that improves hydrolysis efficiency. Despite many studies in this area, the relation of benefit over cost of PEG addition remains unclear. This article describes principles for expressing the effect of PEG as an equivalent enzyme amount, by merging PEG adsorption kinetics with a standardized enzyme dosage response. This model allows cost optimization of PEG addition by marginal analysis, as a function of enzyme dosage, solids concentration and price-ratio of enzyme and PEG. The model is based on the novel observations that the relative increase in apparent enzyme dosage by PEG addition is constant regardless of the absolute enzyme dosage, and that the increase correlates linearly with adsorption of PEG on hydrothermally pretreated wheat straw. The optimum ranged for most cases between 7 and 14 mg PEG per g substrate. The addition of PEG was attractive only above a threshold price-ratio, which decreased from 7.0–1.4 as enzyme dosage increased from 2 to 10 cost units per g substrate, showing that the incentive for introducing PEG to the process becomes stronger as the enzyme dosage increases.
Optimization of oxygen transfer in fermentation of Paecilomyces variotii
(2024-09-28) Leino, Elina
School of Chemical Engineering | Master's thesis
In aerobic fermentations, optimization of oxygen transfer is essential to achieve high productivity in an energy efficient manner. This thesis aimed to calibrate an oxygen transfer model for the fermentation of Paecilomyces variotii and use the model to evaluate energy efficiency. In this thesis, a total of two oxygen transfer models were calibrated for the fermentation of P. variotii: the ideally mixed model (one-compartment) and the two-compartment model. The goal was to understand and evaluate the scalability of the models on an industrial scale. The models tended to simulate oxygen transfer in different ways on an industrial scale. The ideally mixed model tends to overestimate oxygen transfer rate (OTR), whereas the two-compartment model generally underestimates OTR. In reality, OTR is something between these models. The results of the models were indicative and will certainly work for bioreactors of the same size. However, the scalability of the models on an industrial scale should be viewed critically. High oxygen concentrations in the growth broth are expensive to achieve and maintain, as it requires energy. Oxygen transfer models were used to evaluate the energy efficiency of agitation, aeration, and pressure to enhance oxygen transfer on an industrial scale. According to energy efficiency analysis, an increase in pressure linearly increases the energy efficiency of oxygen transfer. Consequently, the most energy efficient way was to keep the pressure at maximum (2 barg). Optimum agitation and gas flow depended on the used oxygen transfer model. The optimum gas flow was between 0.10-0.12 VVM, and the optimum agitator power consumption varied between 0-0.43 kW/m3. However, the scalability of the models is uncertain, and therefore, agitation and gas flow should be dimensioned for a much wider range than the optimum operating point. Moreover, this thesis aimed to compare the effect of tube, ring, and sintered sparges on oxygen transfer. The problem is that P. variotii accumulates in the ring sparger, blocking the gas flow. It was found that the sparger type has little or no effect on oxygen transfer if gas is dispersed via the cavity. Consequently, a tube sparger can be used to solve clogging problems in the fermentation of P. variotii.
Pretreatment categories, process alternatives and material characteristics in enzymatic hydrolysis of lignocellulose
(2016) Pihlajaniemi, Ville
School of Chemical Technology | Doctoral dissertation (article-based)
Fractionation of lignocellulose materials to sugars is a major strategy for the production of renewable fuels and chemicals. This study compares the potential of two major pretreatment categories, hydrothermal treatment and delignification, and contributes to scientific understanding of the phenomena behind enzymatic hydrolysability of wheat straw. Delignification was found to allow higher sugar yields. Since enzyme consumption is a key cost of the fractionation process, the optimal yield target depends on enzyme price. To allow yield optimization, a novel empirical model was developed for the process sugar yield as a function of enzyme consumption and hydrolysis time. The usability of the model was demonstrated by comparing the feasibility of different process alternatives for fractionation. The changes in the material properties of lignocellulose by pretreatments were correlated to cellulose hydrolysability, and for the first time, the importance of the different properties was determined statistically. In the order of importance, the hydrolysis yield depended on cellulose surface area, pore accessibility, lignin content, lignin surface chemistry, cellulose crystallinity and hemicellulose content. During enzymatic hydrolysis, the surface area of cellulose correlated linearly with the total cellulose content, but contrary to expectations, hydrolysis did not reveal fresh lignin surfaces. Different rate constraining mechanisms were incorporated in a Michaelis-Menten type kinetic model, and it was found that permanent hydrolysis-dependent enzyme inactivation should be included with the previously well-established effects of product inhibition and reduction of hydrolysability. For improving fractionation processes, different technological solutions were studied. A flow through process was found to improve fractionation by delignification, but no additional improvement was achieved by counter-current operation. By studying and simulating the packing density and flow properties of a packed straw bed, a flow-through process was found to be possible without clogging the straw bed by compaction. The height of an industrial scale column is restricted by the applicable flow rate. With the simulation model, it was possible to determine the maximum volumetric throughput as a function of column height. Recycling of the solid residue during enzymatic hydrolysis was found to be inefficient for enzyme recycling, but efficient for product removal, with similar benefits as sequential hydrolysis. Both processes significantly improved the volumetric productivity of hydrolysis by increasing the solids concentration without reducing yield. Alternatively, this benefit could be redirected into increasing the yield by maintaining reaction volume with additional water, leading to dilution of the hydrolysis conditions.
Rate-constraining changes in surface properties, porosity and hydrolysis kinetics of lignocellulose in the course of enzymatic saccharification
(2016) Pihlajaniemi, Ville; Sipponen, Mika Henrikki; Kallioinen, Anne; Nyyssölä, Antti; Laakso, Simo
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Background: Explaining the reduction of hydrolysis rate during lignocellulose hydrolysis is a challenge for the understanding and modelling of the process. This article reports the changes of cellulose and lignin surface areas, porosity and the residual cellulase activity during the hydrolysis of autohydrolysed wheat straw and delignified wheat straw. The potential rate-constraining mechanisms are assessed with a simplified kinetic model and compared to the observed effects, residual cellulase activity and product inhibition. Results: The reaction rate depended exclusively on the degree of hydrolysis, while enzyme denaturation or time-dependent changes in substrate hydrolysability were absent. Cellulose surface area decreased linearly with hydrolysis, in correlation with total cellulose content. Lignin surface area was initially decreased by the dissolution of phenolics and then remained unchanged. The dissolved phenolics did not contribute to product inhibition. The porosity of delignified straw was decreased during hydrolysis, but no difference in porosity was detected during the hydrolysis of autohydrolysed straw. Conclusions: Although a hydrolysis-dependent increase of non-productive binding capacity of lignin was not apparent, the dependence of hydrolysis maxima on the enzyme dosage was best explained by partial irreversible product inhibition. Cellulose surface area correlated with the total cellulose content, which is thus an appropriate approximation of the substrate concentration for kinetic modelling. Kinetic models of cellulose hydrolysis should be simplified enough to include reversible and irreversible product inhibition and reduction of hydrolysability, as well as their possible non-linear relations to hydrolysis degree, without overparameterization of particular factors.
Reduction of surface area of lignin improves enzymatic hydrolysis of cellulose from hydrothermally pretreated wheat straw
(2014) Sipponen, Mika; Pihlajaniemi, Ville; Pastinen, Ossi; Laakso, Simo
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Enzymatic hydrolysis of cellulose after pretreatment of wheat straw (WS) was investigated for the first time in relation to lignin surface area (SA). Lignin SA in solid residues from WS autohydrolysis (AH) and successive NH3 (aq) extraction was determined using cationic dye adsorption. AH at increasing severity decreased up to 45% and 53% of WS lignin SA and specific surface area (SSA), respectively. Cellulose-to-glucose conversion from AH solid fractions from 24 h reaction with 15 FPU g−1 cellulase activity increased linearly from 31% to 91% with decreasing lignin SA. When AH solid fractions were extracted with NH3 (aq), both lignin SA and SSA increased in the corresponding solid residues, SSA up to 92%. As a consequence, cellulose-to-glucose conversion decreased in spite of the lower proportion of lignin in the solid residues after the NH3 (aq) extraction. Up to 85% sugar yield was obtained from the single-stage AH process but when combined with NH3 (aq) extraction the two-stage process yielded at most 71% of the original straw sugars. These results show that, independent of the lignin content, reduction of surface area of lignin improves the enzymatic hydrolysis process.
Sellulaasien ja endoksylanaasien toiminnan parantaminen proteiinimuokkauksella
(2014-05-21) Miinalainen, Tuukka
Kemiantekniikan korkeakoulu | Bachelor's thesis
Structural changes of lignin in biorefinery pretreatments and consequences to enzyme-lignin interactions
(2017) Sipponen, Mika; Rahikainen, Jenni; Leskinen, Timo; Pihlajaniemi, Ville; Mattinen, Maija-Liisa; Lange, Heiko; Crestini, Claudia; Österberg, Monika
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The main target of a biorefinery pretreatment process is to break down the lignin-reinforced plant cell wall structure prior to enzymatic hydrolysis of polysaccharides to fermentable sugars. Various physico-chemical alterations occur in lignin during the biomass pretreatment, but effects of those structural changes on subsequent enzymatic hydrolysis have remained ambiguous. We review the reinforcing and detrimental lignin-enzyme interactions and their underlying mechanisms, and use this structure-function information to assess critical features of current and emerging pretreatment technologies. Our perspective is that truly multidisciplinary research is needed to develop pretreatments that render lignin non-inhibiting to enzymes and with high potential for further valorisation.
Value chain analysis of sidestream-based feedstocks for cellular agriculture
(2020-10-20) Voutilainen, Eveliina
Kemian tekniikan korkeakoulu | Master's thesis
The world population will increase above 10 billion by the year 2055, and similarly protein demand will increase by more than 50%. Traditional meat production requires vast quantities of natural resources, and thus new protein sources are required in the future. Cellular agriculture seems a promising solution for protein production, as less land is required compared to traditional meat and plant protein production. This thesis aimed to find potential raw materials for the production of lignocellulosic sugar and food-grade microbial protein, compare lignocellulosic sugar production by using two optional pretreatment methods and to compare four microbial protein processes. A raw material survey was conducted by searching potential raw materials, their properties, and capacities. Lignocellulosic sugar and microbial protein production were evaluated by performing techno-economic analyses. Critical parameters in the processes were determined by sensitivity analysis. Straw, forest-industry sidestreams and surplus grass were seen as potential raw materials, because of the high carbohydrate content, high annual availability and low cost. The production costs of lignocellulosic sugar was lower for the steam explosion than the ammonia process. Protein production costs were the lowest for the Pekilo and Torula. Pekilo process appeared to be the most profitable process, as the lowest production costs and the highest gross profit, IRR, and NPV. The most crucial parameters in the production were enzyme and raw material prices, yield, and investment. As assumed in the beginning of the study, lignocellulose sugars remain elusively more expensive than traditional sugar for biotechnological production. However, these vast raw materials may become increasingly important in the future as the demand for arable land increases due to demand for food. Also it was concluded, that production of edible microbial protein can be profitable for Pekilo process and for other processes by optimization, increasing the selling price or valuing the by-products from the process higher, and if the food-grade safety is guaranteed. Production costs by using alternative raw materials must be studied to decrease costs. Readily fermentable sidestreams might be more profitable than lignocellulosic sidestreams in biotechnological production.