Refining pulp for tensile strength

Increased tensile strength of paper is a primary objective of low consistency refining. Although refining is typically controlled by Specific Refining Energy and Specific Edge Load, these parameters are not independent because both depend directly on power. To overcome this shortcoming, we derived simplified expressions for the number and intensity of impacts on pulp. The number of impacts reflects the capacity of the refiner to impose loading cycles on pulp. The intensity, combined with a response parameter, reflects the probability of a successful refining event at each impact. Based on these parameters, we employed an equation based on cumulative probability to predict tensile strength of pulp after refining. Non-linear fits of this equation to data from the literature for a wide range of pulps refined by various refiners gave response parameters that were remarkably similar ranging from 1.6 – 3.3 × 10 − 6 1.6\text{--}3.3\times {10^{-6}} kg/J. The resulting probability of successful refining events at each impact was found to be quite small, about 1–3 %. We postulated that this is likely due to most force being imposed at fibre crossings in the pulp network. Consequently, multiple cycles are required to expose other parts of fibres and new fibres to loadings. In summary, this new approach to characterizing refining reflects the stochastic nature of the process and enables a direct quantitative link between refiner operation and fibre development.

Fibre development in an intensified mechanical pulping process

Mechanical pulp for printing paper can be produced with a process that involve much less equipment and that require much lower specific energy compared to conventional processes. Even though common evaluation methods, e.g. handsheet testing, have shown that the pulp quality is similar for the simplified and the conventional processes, it is not known how fibre properties, at the microscopic level, is developed with the simplified process. In this mill scale study, the fibre properties attained with an “intensified” mechanical pulping process, consisting of single stage high consistency double disc refining followed by two stage low consistency refining and no reject treatment was investigated. The simplified process was compared to a process with a reject system. The simplified process rendered fibres with higher degree of fibrillation, higher share of axial splits, lower fibre wall thickness but slightly lower length than the conventional process. The fibrillar fines size distribution of the two processes was different. The conventional process generated more of small fibrillar fines which probably explains the higher tensile index at given density for that process. The results show that it is possible to simplify the production process for mechanical pulp and reduce the specific energy with over 700 kWh/adt.

Genome-wide identification of the expansin gene family reveals that expansin genes are involved in fibre cell growth in cotton

Background : Expansins ( EXPs ), a group of proteins that loosen plant cell walls and cellulosic materials, are involved in regulating cell growth and diverse developmental processes in plants. However, the biological functions of this gene family in cotton are still unknown. Results: In this paper, we identified a total of 93 expansin genes in Gossypium hirsutum . These genes were classified into four subfamilies, including 67 GhEXPAs , 8 GhEXPBs , 6 GhEXLAs , and 12 GhEXLBs , and divided into 15 subgroups. The 93 expansin genes are distributed over 24 chromosomes, excluding Ghir_A02 and Ghir_D06. All GhEXP genes contain multiple exons, and each GhEXP protein has multiple conserved motifs. Transcript profiling and qPCR analysis revealed that the expansin genes have distinct expression patterns among different stages of cotton fibre development. Among them, 3 genes ( GhEXPA4o , GhEXPA1A , and GhEXPA8h ) were highly expressed in the initiation stage, 9 genes ( GhEXPA4a , GhEXPA13a , GhEXPA4f , GhEXPA4q , GhEXPA8f , GhEXPA2 , GhEXPA8g , GhEXPA8a , and GhEXPA4n ) had high expression during the fast elongation stage, and GhEXLA1c and GhEXLA1f were preferentially expressed in the transition stage of fibre development. Conclusions: Our results provide a solid basis for further elucidation of the biological functions of expansin genes in relation to cotton fibre development and valuable genetic resources for future crop improvement.

Genome-wide identification of expansin gene family reveals expansin genes are involved in fibre cells growth in cotton

Background : Expansins ( EXPs ), a group of proteins that loosen plant cell walls and cellulosic materials, are involved in regulating cell growth and diverse developmental processes in plants. However, the biological functions of this gene family are still unknown in cotton. Results: In this paper, we identified a total of 93 expansin genes in Gossypium hirsutum . These genes were classified into four subfamilies, including 67 GhEXPAs , 8 GhEXPBs , 6 GhEXLAs , and 12 GhEXLBs , and divided into 15 subgroups. All 93 expansin genes are distributed over 24 chromosomes excluding Ghir_A02 and Ghir_D06. All GhEXP genes contain multiple exons and each GhEXP protein has multiple conserved motifs. Transcript profiling and qPCR analysis revealed that the expansin genes have distinct expression patterns in different stages of cotton fibre development. Among them, 3 genes ( GhEXPA4o , GhEXPA1A , and GhEXPA8h ) were highly expressed in the initiation stage, 9 genes ( GhEXPA4a , GhEXPA13a , GhEXPA4f , GhEXPA4q , GhEXPA8f , GhEXPA2 , GhEXPA8g , GhEXPA8a , and GhEXPA4n ) had high expression during the fast elongation stage, while GhEXLA1c and GhEXLA1f were preferentially expressed in the transition stage of fibre development. Conclusions: Our results provide a solid basis for further elucidation of biological functions of expansin genes in cotton fibre development and valuable genetic resources used for crop improvement in the future.

Genome-wide identification of expansin gene family reveals expansin genes are involved in fibre cells growth in cotton

Background : Expansins ( EXPs ), a group of proteins that loosen plant cell walls and cellulosic materials, are involved in regulating cell growth and diverse developmental processes in plants. However, the biological functions of this gene family are still unknown in cotton. Results: In this paper, we identified a total of 93 expansin genes in Gossypium hirsutum . These genes were classified into four subfamilies, including 67 GhEXPAs , 8 GhEXPBs , 6 GhEXLAs , and 12 GhEXLBs , and divided into 15 subgroups. All 93 expansin genes are distributed over 24 chromosomes excluding Ghir_A02 and Ghir_D06. All GhEXP genes contain multiple exons and each GhEXP protein has multiple conserved motifs. Transcript profiling and qPCR analysis revealed that the expansin genes have distinct expression patterns in different stages of cotton fibre development. Among them, 3 genes ( GhEXPA4o , GhEXPA1A , and GhEXPA8h ) were highly expressed in the initiation stage, 9 genes ( GhEXPA4a , GhEXPA13a , GhEXPA4f , GhEXPA4q , GhEXPA8f , GhEXPA2 , GhEXPA8g , GhEXPA8a , and GhEXPA4n ) had high expression during the fast elongation stage, while GhEXLA1c and GhEXLA1f were preferentially expressed in the transition stage of fibre development. Conclusions: Our results provide a solid basis for further elucidation of biological functions of expansin genes in cotton fibre development and valuable genetic resources used for crop improvement in the future.

Eriodictyol can modulate cellular auxin gradients to efficiently promote in vitro cotton fibre development

Background Flavonoids have essential roles in flower pigmentation, fibre development and disease resistance in cotton. Previous studies show that accumulation of naringenin in developing cotton fibres significantly affects fibre growth. This study focused on determining the effects of the flavonoids naringenin, dihydrokaempferol, dihydroquerectin and eriodictyol on fibre development in an in vitro system. Results 20 μM eriodictyol treatment produced a maximum fibre growth, in terms of fibre length and total fibre units. To gain insight into the associated transcriptional regulatory networks, RNA-seq analysis was performed on eriodictyol-treated elongated fibres, and computational analysis of differentially expressed genes revealed that carbohydrate metabolism and phytohormone signaling pathways were differentially modulated. Eriodictyol treatment also promoted the biosynthesis of quercetin and dihydroquerectin in ovules and elongating fibres through enhanced expression of genes encoding chalcone isomerase, chalcone synthase and flavanone 3-hydroxylase. In addition, auxin biosynthesis and signaling pathway genes were differentially expressed in eriodictyol-driven in vitro fibre elongation. In absence of auxin, eriodictyol predominantly enhanced fibre growth when the localized auxin gradient was disrupted by the auxin transport inhibitor, triiodobenzoic acid. Conclusion Eriodictyol was found to significantly enhance fibre development through accumulating and maintaining the temporal auxin gradient in developing unicellular cotton fibres.

Genome-wide identification of expansin gene family reveals expansin genes are involved in fibre cells growth in cotton

Background : Expansins ( EXPs ), a group of proteins that loosen plant cell walls and cellulosic materials, are involved in regulating cell growth and diverse developmental processes in plants. However, the biological functions of this gene family are still unknown in cotton. Results: In this paper, we identified a total of 93 expansin genes in Gossypium hirsutum . These genes were classified into four subfamilies, including 67 GhEXPAs , eight GhEXPBs , six GhEXLAs , and 12 GhEXLBs , and divided into 15 subgroups. All 93 expansin genes are distributed over 24 chromosomes excluding Ghir_A02 and Ghir_D06. All GhEXP genes contain multiple exons and each GhEXP protein has multiple conserved motifs. Transcript profiling and qPCR analysis revealed that the expansin genes have distinct expression patterns in different stages of cotton fibre development. Among them, three genes ( GhEXPA4o , GhEXPA1A , and GhEXPA8h ) were highly expressed in the initiation stage, nine genes ( GhEXPA4a , GhEXPA13a , GhEXPA4f , GhEXPA4q , GhEXPA8f , GhEXPA2 , GhEXPA8g , GhEXPA8a , and GhEXPA4n ) had high expression during the fast elongation stage, while GhEXLA1c and GhEXLA1f were preferentially expressed in the transition stage of fibre development. Conclusions: Our results provide a solid basis for further elucidation of biological functions of expansin genes in cotton fibre development and valuable genetic resources used for crop improvement in the future.