The effects of boron derivatives as pretreatment chemicals for biodegradation of sunflower stalks

Ayhan Tozluoglu

doi:10.4067/s0718-221x2016005000058

Abstract

This study examined the suitability of boron derivatives as pretreatment chemicals with regard to their efficiency in the enzymatic saccharification of sunflower stalks. It was hypothesized that the utilization of boron derivatives might improve enzymatic digestibility. The aim of this study was to examine the effect of NaOH and the boron derivatives sodium borohydride [NaBH4], calcined tincal [Na2B4O7(1-5)H2O], colemanite [CaB3O4(OH)3H2O], boron oxide [B2O3], borax decahydrate [Na2B4O710H2O], disodium octaborate tetrahydrate [Na2B8O134H2O] and boric acid [H3BO3] on enzymatic saccharification. Results showed that the boron derivatives prevented peeling reactions and preserved more glucan; however, the NaOH removed the highest amounts of xylan and lignin from the structure. Significant xylan removal was observed with H3BO3, while B2O3 was as effective as NaBH4 and NaOH for selective lignin removal. The highest enzymatic saccharification yield (59,5%) resulted with the 2% NaOH pretreatment, whereas slightly lower yields were achieved with some boron derivatives (1% NaBH4-45%; 2% B2O3-40,2%; and 2% H3BO3-36,7%).

Highlights

Sunflower seeds are the third largest source of vegetable oil production, the other valuable sources being soybean and palm (Vaithanomsat et al 2009)
The Na2B4O710H2O pretreated sample had 1,16 times more xylan in the structure compared to the H3BO3 pretreated sample, and Na2B4O710H2O gave an enzymatic yield that was 1,13 times lower. These results indicated that xylan as well as lignin removal had a significant effect on the enzymatic digestibility
Sunflower stalks were treated with NaOH, NaBH4 and the boron derivatives Na2B4O7(1-5)H2O, CaB3O4(OH)3H2O, B2O3, Na2B4O710H2O, Na2B8O134H2O and H3BO3

Summary

Introduction

Sunflower seeds are the third largest source of vegetable oil production, the other valuable sources being soybean and palm (Vaithanomsat et al 2009). Turkey is one of the top ten sunflower-producing countries in the world, with nearly 3 % of the world’s sunflower production and 6 % of the acreage (Anonymous 2014a). Turkish sunflower acreage and crop production have increased from 500000 to 600000 ha and from 800000 to 1,4 million tons, respectively (Anonymous 2014b). The huge volume of these lignocellulose residues (3-7 tons of dry matter/ha) emerging annually (Marechal and Rigal 1999) can become an important low-cost source of materials that can be converted into valuable products such as ethanol. The industrial use of this substrate in bioethanol production may result in decreasing the soil and air pollution associated with the disposal of the stalks

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Conclusion