Stalk Sugar Research Articles

Does increasing plant population density alter sugar yield in high stalk-sugar maize hybrids?

Escalating demands for food and green energy have renewed interest in the dual-purpose use of maize (Zea mays L.) for a biofuel and high-energy forage crop. Recently, maize hybrids with high stalk-sugar (sugarcorn) have been developed. It is important to determine how agronomic practices, for example altering plant population density (PPD), affect stalk-sugar yields of these newly developed hybrids and to advance knowledge required for producing sugarcorn as a dual-purpose bioenergy–high energy silage crop in short-season regions unable to grow sugarcane. A field experiment was conducted for 3 years to assess the effect of PPD on stalk-sugar accumulation, dry matter production, silage and sucrose yields of sugarcorn compared with two commercial silage hybrids. Targeted PPD ranged from 75 000 to 150 000 plants ha–1 in increments of 25 000 plants ha–1. We found that increasing PPD from 75 000 to 125 000 plants ha–1 increased stalk sugar concentrations by up to 25% in some of the sugarcorn hybrids, with minimum change in the conventional check hybrids. The sugarcorn hybrid CO348 × C103 had the highest stalk sugar concentration (128 g kg–1) and sucrose yield of up to 3.8 Mg ha–1 at the targeted PPD of 125 000 (or actual 118 000 ± 7000) plants ha–1. By contrast, the check silage hybrids produced at most 2.0 Mg ha–1 of sucrose yield with much lower stalk sugar concentrations (53–65 g kg–1). Sugarcorn hybrids had generally lower grain yield with greater plant barrenness (the failure of a plant to produce a normal ear) and severer head smut infestation than the conventional silage hybrids. Our results suggest that as a silage crop, the current recommended PPD of 75 000–85 000 plants ha–1 for commercial silage maize production in the region is likely suitable for sugarcorn, and a higher PPD is required if sugarcorn hybrids are designated as a biofuel crop or for dual-purpose use.

A multiple harvest cultivation strategy for ethanol production from sweet sorghum throughout the year in tropical ecosystems

Sweet sorghum is a sugar rich crop that has been considered an alternative feedstock to sugarcane for ethanol production. A full year production cycle is possible as sweet sorghum is capable of multiple harvests. In this work we present experimental results for stalk biomass and sugar productivities, individual sugar distribution at harvest, ethanol yield and productivity of several sweet sorghum varieties and three harvests, the first cut during the rainy period and two ratoon crops during the dry season. The fresh stalk biomass productivity was different among varieties and harvests. All varieties had a lower than expected first harvest productivity, short waterlogging periods during the rainy period might have been the cause, and Top 76-6 showed the best value, 118 Mg per ha. The stalk sugar content dropped drastically for the second ratoon crop which also had an atypical sugar distribution, sucrose content decreased and reducing sugars increased, a premature harvest might have been the possible cause. Umbrella and Top 76-6 had the highest sugar productivity around 10 Mg per ha year. Fructose was the only remaining sugar after fermentation. Top 76-6 showed the highest ethanol productivity of around 4800 L per ha year and the best overall process efficiency.

Characterization of Ethiopian Sweet Sorghum Accessions for 0Brix, Morphological and Grain Yield Traits

The improvement of sweet sorghum (Sorghum bicolor) for biofuel traits is getting more attention globally due to its sugar-rich stalk that can be used as a renewable energy product. An understanding and proper assessment of biofuel-related traits in sweet sorghum crop is an important step toward the development of superior cultivar. The study was conducted to characterize sweet sorghum collections of Ethiopia for 0Brix degree, some morphological and grain yield traits. A total of 180 accessions were collected and evaluated in two environments. The result revealed wide variability among the accessions collected from different regions. Collections from northern part of Ethiopia (Wello and Tigray) showed significantly high 0Brix mean value while collections from the rest of the regions (Hararge, West Shewa, East Wollega and Gojam) expressed lower 0Brix mean value but higher biomass for stalk sugar yield. Most of the accessions showed higher 0Brix mean value, which is similar to globally known sweet sorghum cultivars. Accessions with high 0Brix degree combined with high biomass traits like stalk diameter and plant height will be an ideal germplasm to be used for biofuel production. Hence, it is imperative to utilize these accessions in sweet sorghum breeding program in order to develop superior sugar-rich sweet sorghum cultivars.

Increasing stalk sucrose in sugarcorn (Zea mays L.): genetic analysis and preliminary breeding

The generation of biofuels from biomass such as corn (Zea mays L.) stalks may be improved by increasing the concentration of available sugar. Understanding the inheritance of high stalk sugar traits is important for the development of new hybrids adapted for this purpose. The genetics associated with high stalk sugar (measured as sucrose equivalents) concentration was investigated by conducting a diallel analysis of six adapted inbred lines varying in stalk sucrose concentration, and a generation mean analysis using high and low sucrose inbred lines as parents tested in multiple years. Changes in stalk sucrose concentrations for six families with repeated cycles of selfing and selection over seven generations was also investigated. Results of the diallel and the generation means analysis of stalk sugar traits revealed that both additive [general combining ability (GCA)] and non-additive gene effects [specific combining ability (SCA)] were important for the inheritance of these traits and their expression was influenced by environment. Additive gene actions were more important than non-additive gene actions for controlling these traits. The study also demonstrated that the hybrid combinations of C103 with 73353 for stalk sucrose and with CO384 for stalk juice may be the best candidates for increasing stalk sugar as these inbreds had high means for these traits with favourable SCA estimates and at least one inbred had high GCA. Substantial increase in stalk sucrose in six different families over seven generations using a pedigree breeding method showed that selection gains could be made following this procedure.

Compost Addition Effects upon Sweet Sorghum Biomass Productivity and Sugar Content

Nitrogen availability generally limits plant growth. In order to reduce consumption of chemical fertilizers in agriculture organic amendments are usually incorporated. Among them compost usage is common. The experimental results presented and discussed below were done in order to find out the effects of compost additions on sweet sorghum biomass productivity and stalk sugar content, employing a partial substitution strategy of inorganic nitrogen by organic nitrogen from compost up to total substitution and at three levels of total nitrogen. We found an increasing positive trend between stalk biomass productivity and compost additions for all nitrogen levels tested. Maximum stalk productivity of 56 and 57 Mg/ha on wet basis were obtained with 100 % compost at 100 and 150 kgN/ha levels respectively. A minimum value of 32 Mg/ha on wet basis was obtained by the first cut sample at 50 kgN/ha employing only inorganic fertilization. The ratoon data was higher than those of the first cut for all cases. A significant linear model was adjusted to the first cut data between pressed juice total sugars and the ratio between reducing sugars and sucrose, which indicated a negative correlation among the variables. The data distribution suggested that compost fertilization induced a low ratio and higher sugar content in the stalk.

High Stalk Sugar Corn: A Potential Biofuel Crop for Canada

One of the most energy efficient systems of biofuel production uses the sugar extracted from sugarcane (Saccharum officinarum L.) for fermentation into ethanol; while sugarcane will not grow in Canada, corn (Zea mays L.), another C4 crop can. The overall objective of our study was to determine if there was corn germplasm, adapted to the short‐season regions of Canada, with high stalk sugar content. Thirty‐nine genotypes from diverse backgrounds were evaluated for stalk sucrose accumulation and associated traits (juice percentage, plant height, weight, and moisture) in field trials from 2007 to 2009. Genotypic differences for stalk sucrose and juice percentage were highly significant. Mean stalk sucrose ranged from 5.1 to 16.4 Brix (oBx) and fresh biomass from 45 to 135 Mg ha−1 suggesting the presence of exploitable genetic variation. Mean stalk sucrose concentration was significantly higher in plants where pollination was prevented. Calculated sucrose yield of experimental hybrids ranged from 4.3 to 6.0 Mg ha−1. At the current conversion efficiency, the products of sucrose and fresh biomass can be translated into 3600 L ha−1 ethanol plus 47 Mg ha−1 silage, indicating that this high stalk sugar corn (or “sugarcorn”) would be a valuable and an economically viable crop for Canada and elsewhere.

Mapping dynamic QTL of stalk sugar content at different growth stages in maize

The stalk sugar content in silage maize plays an important role in improving its forage quality and palatability. In this study, we reported a dynamic quantitative trait loci (QTL) analysis of stalk sugar content at different growth stages in maize. A recombinant inbred line (RIL) population with 202 lines derived from a cross of YXD053 × Y6-1 was used to identify the dynamic QTL for stalk sugar content (Brix) in maize. The Brix of RILs were measured at four stages in two environments. Twenty-two QTLs affecting maize stalk sugar content (Brix) were detected by unconditional mapping method. Fifteen QTLs were identified using conditional mapping approach. No QTL was detected at all sampling stages. Six QTL, qSSC-2.1, qSSC-2.2, qSSC-2.3, qSSC-5.1, qSSC-9.1 and qSSC-9.4, were detected by both unconditional and conditional mapping. One major QTL qSSC-2.1 flanked by markers bnlg1909 and umc1635 on chromosome 2 had a relatively high net effects of gene expression from anthesis stage to 20 days after anthesis. A total of six pairs of QTL with significant epistatic effects were identified at different developmental stages. No significant QTL × environment interactions were observed. Stalk sugar content is controlled by a complex genetic mechanism, and the QTL detected at different development stages might be important contributors to stalk sugar content in maize.

Genetic variability among sorghum accessions for seed starch and stalk total sugar content

Sorghum (Sorghum bicolor (L.) Moench) is a staple food grain in many semi-arid and tropical areas of the world, notably in sub-Saharan Africa because of its adaptation to harsh environments. Among important biochemical components for sorghum for processors are the levels of starch (amylose and amylopectin) and total sugar contents. The aim of this study was to determine the genetic variation for total starch in the seed, its components and total sugar in the stalks of the sorghum accessions from Ethiopia and South Africa. Samples of 22 sorghum accessions were evaluated. Significant variations were observed in total starch (31.01 to 64.88 %), amylose (14.05 to 18.91 %), the amylose/amylopectin ratio (0.31 to 0.73) and total stalk sugar content (9.36 to 16.84 %). Multivariate analysis showed a wide genetic variation within and among germplasm accessions which could be used in the selection of parental lines for the improvement of traits of interest through breeding. The variation found among the sorghum accessions shows that an improved total starch and starch components and stalk sugar contents can be achieved through crossing these selected genotypes.

Genetic Variability and Effect of Postflowering Drought on Stalk Sugar Content in Sorghum Mini Core Collection

ABSTRACTSweet sorghum [Sorghum bicolor (L.) Moench] is an important food, feed, and biofuel crop worldwide. Its stalks are rich in sugar, largely influenced by environments and crop stage when the stalks are harvested. This study evaluated sorghum mini core collection for stalk sugar content on the basis of Brix, phenology, and agronomic traits. Accessions were first classified into five groups based on flowering to match crop phenology, which together with controls were separately grown in split‐plot design in vertisol under irrigated and drought stress conditions for two postrainy seasons. The main and interaction effects were significant for most of the traits. Drought stress significantly increased the mean Brix (12.11 to 26.76%) in four of the five groups of accessions. The mean Brix increased under drought in 169 accessions, decreased in one accession, while the remaining accessions were not affected. IS 13294, 13549, 23216, 23684, 24139, 24939, and 24953 significantly recorded greater mean Brix (14.0 to 15.2%) as compared with best control, IS 33844 (12.4%), across environments. However, these accessions had lower yields and lower 100‐seed weight. In contrast, IS 1004, 4698, 23891, and 28141 significantly outyielded IS 33844 by 11.7 to 22.7% and had almost the same Brix content (∼13%). A hierarchical tree diagram grouped these accessions into two distinct clusters: accessions with significantly greater Brix but lower yield and those with high yield but with Brix similar to IS 33844. The grouping also separated accessions largely on the basis of geographic regions and racial classification. The identified accessions are ideal resources for the development of cultivars with bioenergy traits.

Study on Sugar Production Conditions of Dilute Sulfuric Acid Hydrolysis of Corn Straw

In this paper, through the study of reducing sugar conditions of corn straw hydrolysis under acidic condition, looking for the production of experimental conditions relatively reasonable. Mainly by dilute sulfuric acid hydrolysis of corn straw by single factor test, effects of sulfuric acid concentration, temperature, reaction time, particle size, ratio of solid to liquid five factors, effects on sugar yield of corn straw. The dilute sulfuric acid concentration 5%, ratio of solid to liquid was 1:14, when the reaction time is 140 min, particle fineness of 120 mesh, the reaction temperature is 100 °C, corn stalk sugar yield reached a maximum 20.11%.

Enzymatic hydrolysis enhancement of corn lignocellulose by supercritical CO2 combined with ultrasound pretreatment

Supercritical carbon dioxide (scCO2) combined with an ultrasound method using 15–25 MPa and the temperature range of 120–170 °C for 0.5–4 h was proposed as a pretreatment for corn cob and corn stalk with moisture contents of 50%. The results showed that both scCO2 pretreatment and scCO2 combined with ultrasound pretreatment could improve the total reducing sugar yields of the two materials. Enzymatic hydrolysis of both corn cob and corn stalk sugar using scCO2 pretreatment was increased by 50% and 29.8% compared with the control samples, respectively, while they were increased by 75% and 13.4%, respectively, using the scCO2 combined with ultrasound pretreatment under our experimental conditions. Following treatment from the two pretreatment processes, X-ray diffraction results indicated no significant change in crystallinity of the two materials. However, scanning electron microscopy images demonstrated that the microscopic structure of lignocellulose changed considerably and the surface area of lignocellulose increased significantly.

Identification of QTL for stalk sugar-related traits in a population of recombinant inbred lines of maize

Increasing sugar content in silage maize stalk improves its forage quality and palatability. The genetic mapping and characterization of quantitative trait loci (QTLs) is considered a valuable tool for trait enhancement, yet little information on QTL for stalk sugar content in maize has been reported. To this end, we investigated QTLs associated with stalk sugar traits including Brix, plant height (PHT), three ear leaves area (TELA), and days to silking (DTS) in two environments using a population of 202 recombinant inbred lines from a cross between YXD053, which has a high stalk sugar content, and Y6-1, which has a low stalk sugar content. A genetic map with 180 SSR and 10 AFLP markers was constructed, which spanned 1,648.6 cM of the maize genome with an average marker distance of 8.68 cM, and QTLs were detected using composite interval mapping. Seven QTLs controlling Brix were mapped on chromosomes 1, 2, 6 and 9 in the combined environments. These QTLs could explain 2.69–13.08 % of the phenotypic variance. One major QTL for Brix on chromosome 2 located between the markers bnlg1909 and umc1635 explained 13.08 % of the phenotypic variance. Y6-1 also contributed QTL allele for increased Brix on chromosome 6. One major QTLs controlling PHT on chromosome 1 and TELA on chromosome 4 were also identified and accounted for 13.68 and 12.49 % of the phenotypic variance, respectively. QTL alleles for increased DTS were located on chromosomes 1 and 5 of YXD053. Significant epistatic effects were identified in four traits, but no significant QTL × environment interactions were observed. The information presented here may be valuable for stalk sugar content improvement via marker-assisted selection in silage maize breeding programs.

Ethanol from sweet sorghum in a year-round production cycle

Four sweet sorghum varieties, M81E, Sugar Drip, Top 76-6, and Umbrella, were sowed early in the years 2011 and 2012 in two experimental plots located in the Guatemalan Pacific lowlands within the sugarcane-producing region. Three harvests were done, a first cut and two consecutive ratoon crops. Stalk biomass, stalk sugar content, and proportions of individual sugars in the extracted juice were measured. Ethanol production employing simultaneous sugar extraction from stalk particles and fermentation by a commercial yeast strain was carried out in 2011 samples from the first harvest and second ratoon crop. Fresh stalk biomass productivity was the same for the first harvest and the first ratoon crop, but it was dependent on variety and site. The second ratoon crop diminished drastically without exception. Considering only two harvests per year, Top 76-6 had the best overall productivity with a rounded average of 47 Mg/ha/harvest, equivalent to 94 Mg/ha/year, and the higher sugar productivity, equal to 5,285 kg/ha/harvest or approximately 11 Mg/ha/year. Proportions of individual sugars at harvest varied among varieties, sites, and year, and three sample groups were identified by hierarchical clustering. An inverse correlation was found between stalk sugar content and the ratio between hexoses and sucrose at harvest, implying that the smaller the ratio, the higher the sugar content. Ethanol production was between 200 and 250 g/ethanol/kg of dry stem for Sugar Drip, Top 76-6, and Umbrella varieties for first harvest samples. The data for the second ratoon crop was lower for all varieties and sites. Ethanol productivity was higher for Umbrella and Top 76-6 and equal to approximately 2,500 L/ha/harvest.

Sweet Sorghum Research and Development in India: Status and Prospects

Renewable energy is a critical source of energy that contributes to energy security, reducing dependence on fossil fuels and emission of greenhouse gases. India would require more than 6.3 billion liters of ethanol to meet its ambitious target of 20 % EBP by 2017. Sweet sorghum is a promising dryland adapted biofuel feedstock that addresses food-versus-fuel issue favourably. Owing to its genetic variability in terms of stalk sugar traits such as total soluble sugars, green stalk yield, juice quantity and grain yield various research institutes in India and abroad have developed superior varieties and hybrids. Two commercial sweet sorghum based distilleries were established in India but could not operate for long for several reasons. The decentralized crushing units were established to overcome the issues encountered by centralized units. The large scale cultivation of sweet sorghum can happen if improved cultivars with higher sugar yield with multiple biotic and abiotic stress tolerance are available besides more importantly the policy support from Government of India in terms of both producer and processor incentives materialize.

A Cost-effective Integrated Process to Convert Sweet Sorghum Stalks into Biofuels

Biofuel is a renewable and sustainable energy as an substitute of fossil fuel. In China, the key challenge to develop biofuels is how to balance the competition of food and bioenergy and supply a sustainable feedstock. Sweet sorghum is highlighted as a multiple platform plant which can supply grain, sugar, cellulose and feed. In addition, sweet sorghum has so good tolerance of drought and sterilize that it can grow on marginal land. However, the loose stalk pith of sweet sorghum results in the infeasibility of liquid fermentation technology due to the considerably high energy consumption.In present research, an integrated process combined advanced solid-state fermentation technology (ASSF) and alkaline pretreatment was presented in this work. Soluble sugars in sweet sorghum stalks were firstly converted into ethanol by ASSF using crushed stalks directly. Then, the operation combining ethanol distillation and alkaline pretreatment was performed in one distillation-reactor simultaneously. The process was optimized according to the yield of sugar-ethanol and amounts of monosaccharide released from SSB. In our novel process, energy consumption of mechanically squeeze and pretreatment of SSB was avoided. Meanwhile, the recalcitrance of lignocellulose was destructed and the biodegradation of lignocellulose into chemical products is feasible to achieve. Cellulosic ethanol as a model product was studied by using this novel integrated process. The mass balance of the overall process was calculated, and 91.9kg was achieved from one tonne of fresh sweet sorghum stalk. Energy consumption for raw materials preparation and pretreatment were reduced or avoided in our process. To produce 1 tonne of ethanol, the energy input in this process was 12,481.2MJ/tonne, while the energy input in other cellulosic ethanol processes is from 17,430 to 33,330MJ/tonne.Based on this technology, the recalcitrance of lignocellulose was destructed via a cost-efficient process and structural carbohydrates in sweet sorghum stalks were hydrolysed into fermentable sugars. Bioconversion of fermentable sugars released from sweet sorghum bagasse into different products except ethanol, such as butanol, biogas, and chemicals was feasible to operate under low energy-consumption conditions. So it is considered as a promising process to produce biofuels at commercial scale.

The Cultivation Technique for Increasing the Stalk Sugar Content of Energy Plant Sweet Sorghum in Yellow River Delta

This study was carried out to investigate the suitable technique for increasing the stalk sugar content of two sweet sorghum cultivars (salt-tolerant cultivar Jitianza 2 and salt-sensitive cultivar Lvneng 1) in saline soils of Yellow River Delta. Stalk sugar content of sweet sorghum in saline soil was significantly increased using the following integrated cultivation technique: (1) increasing organic fertilizer level; (2) applying optimum phosphorus and potassium fertilizer; (3) surface fertilizer application; (4) cultivating salt-tolerant sweet sorghum cultivars; (5) planting with plastic mulching; (6) planting in the early of the optimum seedling time (sowing as early as possible); (7) removing tillers during seedling stage; (8) cutting spike by half-strength before flowering. Jitianza 2 had higher stalk Brix than Lvneng 1 under the same cultivation condition. Therefore, planting salt-tolerant sweet sorghum cultivars in saline soil combined with these integrated cultivation techniques can get higher stalk sugar content in Yellow River Delta of China, which was beneficial for energy alcohol production from sweet sorghum.

Effect of Different Crushing Treatments on Sweet Sorghum Juice Extraction and Sugar Quality Traits in Different Seasons

Sweet sorghum (Sorghum bicolor (L.) Moench) is an important biofuel crop that produces both food (grain) and biofuel (from stalk juice). The objective of this investigation was to assess the effect of different crushing treatments on juice extraction and sugar quality traits of sweet sorghum cultivars grown in different seasons. Three sweet sorghum cultivars along with three stalk crushing treatments namely (i) stalk only crushed (leaf, sheath and panicle removed), (ii) stalk plus sheath crushed (leaf and panicle removed), and (iii) whole plant crushed (but only panicle removed) were assessed in split–split-plot design during 2009 rainy (Kharif) and 2009 post-rainy (Rabi) seasons. The percent juice extraction and juice sugar quality traits were significant (P ≤ 0.05) in different crop seasons, but were non-significant among cultivars and crushing treatments. Sweet sorghum cultivars grown during rainy season had significantly higher total soluble sugars (TSS), sucrose and purity per cent than in post-rainy season. Experimental variety SPSSV 30 showed significant superiority by 25 % in TSS and sucrose content than check namely CSH 22SS. Effect of crushing treatments on juice extraction and sugar quality traits were non-significant except juice brix. It is recommended that the complete sweet sorghum stalks after removing the panicle can be crushed without the need for removing leaf and sheath both in large research trial samples, and bulk harvested stalks at biofuel processing facility. This will reduce processing time at the sugar mill and helps avoiding rapid deterioration of stalk sugars in the ambient field condition, as removal of leaf and sheath in sweet sorghum is highly cumbersome unlike sugarcane, where it is relatively easy.

Association analysis of sugar yield-related traits in sorghum [Sorghum bicolor (L.)

Association mapping is widely used for detecting QTLs in higher plants. In the present study a synthetic sorghum population containing 119 representative samples, including 43 sweet and 76 grain sorghum accessions originating mainly from China, USA and India, were genotyped using 51 simple-sequence repeat (SSR) markers. Linkage disequilibrium (LD) of pair-wise loci and population structure were analyzed, followed by association analysis of SSR loci and 3 sugar yield related traits using the TASSEL general linear model program. Results showed that: (i) different degrees of LD occurred among syntenic markers and also among nonsyntenic markers, indicating historical recombination among sorghum linkage groups; (ii) significant LD extended up to 7.31 cM; (iii) the collection of accessions was composed of three subgroups; (iv) four marker loci were associated with stalk sugar concentration, fresh stalk weight and stalk juice weight measured in different growing environments and could be used, therefore, in future marker assisted breeding programs. Several loci were also associated with two or more traits simultaneously, which might be due to tight linkage between different genes affecting these traits and/or pleiotropy. In addition, some associated markers were located close to QTLs previously mapped in family-based linkage mapping analyses.

A novel cost-effective technology to convert sucrose and homocelluloses in sweet sorghum stalks into ethanol

BackgroundSweet sorghum is regarded as a very promising energy crop for ethanol production because it not only supplies grain and sugar, but also offers lignocellulosic resource. Cost-competitive ethanol production requires bioconversion of all carbohydrates in stalks including of both sucrose and lignocellulose hydrolyzed into fermentable sugars. However, it is still a main challenge to reduce ethanol production cost and improve feasibility of industrial application. An integration of the different operations within the whole process is a potential solution.ResultsAn integrated process combined advanced solid-state fermentation technology (ASSF) and alkaline pretreatment was presented in this work. Soluble sugars in sweet sorghum stalks were firstly converted into ethanol by ASSF using crushed stalks directly. Then, the operation combining ethanol distillation and alkaline pretreatment was performed in one distillation-reactor simultaneously. The corresponding investigation indicated that the addition of alkali did not affect the ethanol recovery. The effect of three alkalis, NaOH, KOH and Ca(OH)2 on pretreatment were investigated. The results indicated the delignification of lignocellulose by NaOH and KOH was more significant than that by Ca(OH)2, and the highest removal of xylan was caused by NaOH. Moreover, an optimized alkali loading of 10% (w/w DM) NaOH was determined. Under this favorable pretreatment condition, enzymatic hydrolysis of sweet sorghum bagasse following pretreatment was investigated. 92.0% of glucan and 53.3% of xylan conversion were obtained at enzyme loading of 10 FPU/g glucan. The fermentation of hydrolyzed slurry was performed using an engineered stain, Zymomonas mobilis TSH-01. A mass balance of the overall process was calculated, and 91.9 kg was achieved from one tonne of fresh sweet sorghum stalk.ConclusionsA low energy-consumption integrated technology for ethanol production from sweet sorghum stalks was presented in this work. Energy consumption for raw materials preparation and pretreatment were reduced or avoided in our process. Based on this technology, the recalcitrance of lignocellulose was destructed via a cost-efficient process and all sugars in sweet sorghum stalks lignocellulose were hydrolysed into fermentable sugars. Bioconversion of fermentable sugars released from sweet sorghum bagasse into different products except ethanol, such as butanol, biogas, and chemicals was feasible to operate under low energy-consumption conditions.

Inheritance Analysis of Stalk Sugar Content in Maize

Increasing sugar content in silage maize stalk improves forage quality and palatability. However, the mechanism of inheritance of stalk sugar content in maize has not been clear yet. To this end, joint analysis of a mixed genetic model of both major gene and polygene was conducted to investigate the inheritance of stalk sugar content in maize. Maize inbred lines YXD053 (high sugar content, Brix = 11.32%), 98A-04 (high sugar content, Brix = 10.69%), and Y6-1 (low sugar content, Brix = 6.3%) were used as parents in this study. Stalk sugar content of three parents and four populations of F 1 , F 2 , BC 1 , and BC 2 generated from two crosses of YXD053×Y6-1 and 98A-04×Y6-1, was surveyed. Results showed that sugar content in maize stalk was controlled by two major genes with additive-dominance-epistatic effects and polygene with additive-dominance-epistatic effects, and mainly governed by major genes. For cross YXD053×Y6-1, the heritabilities of major genes in BC 1 , BC 2 , and F 2 were 34.52%, 52.94%, and 73.05%, respectively. The heritability of polygene could only be detected in BC 2 , which was 23.87%. For cross 98A-04×Y6-1, the heritabilities of major genes in BC 1 , BC 2 and F 2 were 60.49%, 28.79%, and 68.62%, respectively. The heritability of polygene was not detected in F 2 . The total heritability of major gene and polygene for crosses YXD053×Y6-1 and 98A-04×Y6-1 was 61.46% and 69.94%. The degree of dominance of major gene (h/d) in two crosses was less than one, and the additive genetic effects might play a more important role in breeding of hybrids with high stalk sugar content. Additionally, sugar content in maize stalk could be also subject to environmental factors. Results presented here provide valuable information for stalk sugar content improvement in silage maize breeding program, and lay a foundation for the following maize stalk sugar content QTLs mapping.