Telaah Potensi Penerapan Teknologi Terkini pada Hidrolisis Selulosa dengan Sistem Pengendalian Terintegrasi dalam Proses Bioetanol G2

Kajian ini merangkum teknologi dan inovasi sistem pengendalian yang berpotensi diterapkan dalam intensifikasi proses hidrolisis selulosa pada produksi bioetanol G2. Telaah dimulai dari perkembangan terbaru intensifikasi produksi bioetanol secara umum. Hidrolisis selulosa adalah tahapan pembeda antara proses bioetanol G2 dan generasi sebelumnya. Perhatian utama dalam intensifikasi hidrolisis selulosa adalah pada bagaimana hidrolisis selulosa terintegrasi dengan sistem pengendalinya dan integrasi hidrolisis selulosa dengan bagian hulu (pretreatment) dan hilir (penyulingan). Keunikan proses ini adalah durasi kerja yang membutuhkan 48 jam dan viskositas campuran yang tergantung waktu. Bagian akhir telaah ini memetakan potensi penerapan teknologi dan inovasi terbaru yang telah dirangkum. Pemetaan berdasarkan potensi peningkatan efisiensi dan potensi tambahan investasi. Sakarifikasi Very High Gravity (VHG) pada kecepatan pengadukan optimum dan intermitten dinilai sebagai pilihan paling menarik bila intensifikasi dilakukan pada unit produksi yang telah berdiri. Namun jika intensifikasi untuk rancangan pabrik baru, maka tangki hidrolisis yang dirancang dengan simulasi CFD, dilengkapi dengan sekat (baffles) yang bergerak terkendali, dan rancangan batang pengaduk (impeller) paling cocok menurut simulasi adalah pilihan menarik. Rancangan ini kemudian diintegrasikan dengan sistem pengendali yang mampu memperkirakan perubahan viskositas. Review on Potency of Application Recent Technology in the Integrated Process and Control on Cellulose Hydrolysis in Bioethanol G2 Production ProcessAbstractThis review listed current technologies and innovations in the control system which potentially applied in the intensification of cellulose hydrolysis as part of 2nd Generation Bioethanol production process. The review started from the general latest innovations in the 2nd Generation Bioethanol. Cellulose hydrolysis as the main characteristics in the 2nd Generation of Bioethanol required further attention in the intensification. Especially in how to integrate cellulose hydrolysis with its control system and to integrate it with upstream and downstream units. The special requirements in cellulose hydrolysis are 48 hours agitation duration and time-dependent mixture viscosity. At the end of the review, listed technologies were assessed to be applied in the 2nd Generation Bioethanol. The assessment was based on their potency in increasing process efficiency and the potency of required investment if they are applied. A Very High Gravity (VHG) saccharification at optimum intermittent agitation speed was a promising innovation for cellulose hydrolysis if intensification was conducted onto the existing production plant. If intensification is conducted to a plant design, building an agitation tank according to best Computational Fluid Dynamic (CFD) simulation, complemented with controlled moving baffles and best suitable impeller design is a promising design for efficient hydrolysis. This agitation tank was then completed with the advanced available control system, which is capable to adapt the viscosity changes.

Very High Gravity Bioethanol Revisited: Main Challenges and Advances

Over the last decades, the constant growth of the world-wide industry has been leading to more and more concerns with its direct impact on greenhouse gas (GHG) emissions. Resulting from that, rising efforts have been dedicated to a global transition from an oil-based industry to cleaner biotechnological processes. A specific example refers to the production of bioethanol to substitute the traditional transportation fuels. Bioethanol has been produced for decades now, mainly from energy crops, but more recently, also from lignocellulosic materials. Aiming to improve process economics, the fermentation of very high gravity (VHG) mediums has for long received considerable attention. Nowadays, with the growth of multi-waste valorization frameworks, VHG fermentation could be crucial for bioeconomy development. However, numerous obstacles remain. This work initially presents the main aspects of a VHG process, giving then special emphasis to some of the most important factors that traditionally affect the fermentation organism, such as nutrients depletion, osmotic stress, and ethanol toxicity. Afterwards, some factors that could possibly enable critical improvements in the future on VHG technologies are discussed. Special attention was given to the potential of the development of new fermentation organisms, nutritionally complete culture media, but also on alternative process conditions and configurations.

Novel Effective Yeast Strains and Their Performance in High Gravity and Very High Gravity Ethanol Fermentations from Sweet Sorghum Juice

Yeasts were isolated from four potential sources, sweet sorghum juice, sugar cane juice, grapes and rambutan. The 27 yeast isolates were tested for their ethanol tolerance (15% v/v of ethanol) and ethanol fermentation performance in a synthetic ethanol production medium (200 g/L of total sugar). Only five isolates, SCJ04KKU, SCJ07KKU, SCJ09KKU, SCJ14KKU and SSJ01KKU could tolerate 15% ethanol and produce ethanol at levels higher than 55 g/L. The ethanol production efficiency from sweet sorghum juice under high gravity (HG, 200 and 240 g/L of total sugar) and very high gravity (VHG, 280 g/L of total sugar) conditions of the five isolates was tested. Saccharomyces cerevisiae NP01 and S. cerevisiae ATCC4132 were used as reference strains. The results showed that the SSJ01KKU isolate gave the highest ethanol production efficiency under all conditions. Ethanol concentration (PE), yield (YP/S) and productivity (QP) values were 98.89 g/L, 0.50 and 1.18 g/L·h, respectively, with sugar consumption (SC) of 98.96% under the HG condition at 200 g/L of total sugar. Under the HG condition at 240 g/L of total sugar, the PE, YP/S and QP values were 118.12 g/L, 0.51 and 1.41 g/L·h, respectively, with the SC of 95.79%. These values were 82.29 g/L, 0.34 and 0.98 g/L·h, respectively, with the SC of 85.59% under the VHG condition. Addition of urea into the sweet sorghum juice under all conditions significantly shortened the fermentation time, resulting in increased QP values. Based on molecular taxonomic analysis of the five isolates using sequence analysis of the D1/D2 domain and the ITS1 and ITS2 regions, SSJ01KKU is S. cerevisiae, whereas SCJ04KKU, SCJ07KKU, SCJ09KKU and SCJ14KKU are Pichia caribbica.

Wheat gluten hydrolysates promotes fermentation performance of brewer’s yeast in very high gravity worts

The effects of wheat gluten hydrolysates (WGH) and their ethanol elution fractions obtained on XAD-16 resin on physiological activity and fermentation performance of brewer’s yeast during very-high-gravity (VHG) worts fermentation were investigated. The results showed that the addition of WGH and their elution fractions in VHG worts significantly enhanced yeast biomass and viability, and further increased the fermentability, ethanol yield and productivity of yeast. Supplementation with 40% ethanol fraction exhibited the highest biomass (6.9 g/L dry cell), cell viability, fermentability (82.05%), ethanol titer (12.19%, v/v) and ethanol productivity during VHG worts fermentation. In addition, 40% ethanol fraction supplementation also caused the most consumption of amino acid and the highest accumulation of intracellular glycerol and trehalose, 15.39% of increase in cell-membrane integrity, 39.61% of enhancement in mitochondrial membrane potential (MMP), and 18.94% of reduction in intracellular reactive oxygen species (ROS) level in yeast under VHG conditions. Therefore, WGH supplementation was an efficient method to improve fermentation performance of brewer’s yeast during VHG worts.

Wheat Gluten Hydrolysates Promotes Fermentation Performance of Brewer’s Yeast in Very High Gravity Worts

The effects of wheat gluten hydrolysates (WGH) and their ethanol elution fractions obtained on XAD-16 resin on physiological activity and fermentation performance of brewer’s yeast during very-high-gravity (VHG) worts fermentation were investigated. The results showed that the addition of WGH and their elution fractions in VHG worts significantly enhanced yeast biomass and viability, and further increased the fermentability, ethanol yield and productivity of yeast. Supplementation with 40% ethanol fraction exhibited the highest biomass (6.9 g/L dry cell), cell viability, fermentability (82.05%), ethanol titer (12.19%, v/v) and ethanol productivity during VHG worts fermentation. In addition, 40% ethanol fraction supplementation also caused the most consumption of amino acid and the highest accumulation of intracellular glycerol and trehalose, 15.39% of increase in cell-membrane integrity, 39.61% of enhancement in mitochondrial membrane potential (MMP), and 18.94% of reduction in intracellular reactive oxygen species (ROS) level in yeast under VHG conditions. Therefore, WGH supplementation was an efficient method to improve fermentation performance of brewer’s yeast during VHG worts.